Method of manufacturing semiconductor device, method of processing substrate and substrate processing apparatus for forming thin film containing at least two different elements

ABSTRACT

Provided are a method of manufacturing a semiconductor device and a substrate processing apparatus. The method includes forming a thin film having a predetermined thickness and a predetermined composition on the substrate, the thin film including a first element and a second element different from the first element, by repeating a cycle a plurality of times, the cycle including: (a) forming a first layer including the first element and having a thickness of several atomic layers or less on the substrate by supplying a gas containing the first element into a process vessel accommodating the substrate under a condition where a chemical vapor deposition (CVD) reaction is caused; and (b) forming a second layer including the first element and the second element by supplying a gas containing the second element into the process vessel to modify the first layer without saturating a modifying reaction of the first layer by the gas containing the second element.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 of Japanese Patent Application No. 2008-300891, filed onNov. 26, 2008, and Japanese Patent Application No. 2009-246707, filed onOct. 27, 2009, in the Japanese Patent Office, the entire contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device manufacturingmethod including a process of forming a thin film on a substrate, and asubstrate processing apparatus.

2. Description of the Prior Art

Among semiconductor device manufacturing processes, there is a processof forming an insulating film such as silicon oxide (SiO₂) film orsilicon nitride (Si₃N₄) film. Since silicon oxide films have goodproperties such as excellent insulation properties and low dielectricconstant, silicon oxide films are widely used as insulating films orinterlayer films. In addition, since silicon nitride films have goodproperties such as excellent insulation properties, corrosionresistance, dielectric constant, and film stress controllability,silicon nitride films are widely used as insulating films, mask films,charge storage films, and stress control films. As a method of formingsuch a film, a chemical vapor deposition (CVD) method or an atomic layerdeposition (ALD) is used.

In recent years, as a result of scaling down of semiconductor devices orlow-temperature substrate processing processes, either in the case wherethe quality of films remains at the conventional level or in the casewhere the quality of films is degraded due to low-temperatureprocessing, it is difficult to ensure the performance of semiconductordevices. Although new kinds of films are being developed to ensure theperformance of semiconductor devices, due to tasks (such as costs andaffections on another process) caused by the development of new kinds offilms, the case of achieving desired performance levels by improvingexisting films is more preferable.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method ofmanufacturing a semiconductor device and a substrate processingapparatus that are designed to modify a conventional film so as toimprove the quality of the film for achieving a desired performancelevel of a semiconductor device.

According to an aspect of the present invention, there is providedmethod of manufacturing a semiconductor device, the method includingforming a thin film having a predetermined thickness and a predeterminedcomposition on the substrate, the thin film including a first elementand a second element different from the first element, by repeating acycle a plurality of times, the cycle including:

-   -   (a) forming a first layer including the first element and having        a thickness of several atomic layers or less on the substrate by        supplying a gas containing the first element into a process        vessel accommodating the substrate under a condition where a        chemical vapor deposition (CVD) reaction is caused; and    -   (b) forming a second layer including the first element and the        second element by supplying a gas containing the second element        into the process vessel to modify the first layer without        saturating a modifying reaction of the first layer by the gas        containing the second element.

According to another aspect of the present invention, there is provideda substrate processing apparatus including:

a process vessel configured to accommodate a substrate;

a first element-containing gas supply system configured to supply a gascontaining a first element to an inside of the process vessel;

a second element-containing gas supply system configured to supply a gascontaining a second element to the inside of the process vessel;

a pressure regulating unit configured to control pressure of the insideof the process vessel; and

a controller,

wherein the controller is configured to control the pressure regulatingunit, the first element-containing gas supply system, and the secondelement-containing gas supply system so as to:

form a first layer including the first element on the substrate bysupplying the gas containing the first element to the inside of theprocess vessel in which the substrate is accommodated under a conditionwhere a CVD reaction is caused;

form a second layer including the first element and the second elementby supplying the gas containing the second element to the inside of theprocess vessel to modify the first layer; and

form a thin film including the first and second elements and having apredetermined thickness by setting the forming of the first layer andthe forming of the second layer to one cycle and repeating the cycle atleast once,

wherein pressure of the inside of the process vessel, or pressure of theinside of the process vessel and a time of supplying the gas in oneprocess of the forming of the first layer and the forming of the secondlayer are controlled to be higher or longer than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the one process when the thin filmhaving a stoichiometric composition is formed, or

pressure of the inside of the process vessel, or pressure of the insideof the process vessel and a time of supplying the gas in the otherprocess of the forming of the first layer and the forming of the secondlayer are controlled to be lower or shorter than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the other one process when the thinfilm having the stoichiometric composition is formed,

so as to form the thin film having a composition that one of the firstand second elements of the thin film is excessive as compared with theother in terms of the stoichiometric composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view schematically illustrating avertical process furnace of a substrate processing apparatus accordingto a preferred embodiment of the present invention.

FIG. 2 is a sectional view taken along line A-A of FIG. 1 forschematically illustrating the vertical process furnace according to apreferred embodiment of the present invention.

FIG. 3 is a view illustrating gas supply timing and plasma power supplytiming in a first sequence according to an embodiment of the presentinvention.

FIG. 4 is a view illustrating gas supply timing in a second sequenceaccording to an embodiment of the present invention.

FIG. 5 is a view illustrating gas supply timing in a third sequenceaccording to an embodiment of the present invention.

FIG. 6 is a schematic view illustrating formation of a silicon nitridefilm on a wafer according to the first sequence of the embodiment of thepresent invention.

FIG. 7 is a schematic view illustrating a case where silicon isexcessively supplied in Step 1 of the first sequence according to theembodiment of the present invention.

FIG. 8 is a schematic view illustrating a case where nitrogen isinsufficiently supplied in Step 2 of the first sequence according to theembodiment of the present invention.

FIG. 9 is a schematic view illustrating formation of a siliconcarbonitride film on a wafer according to the second sequence of theembodiment of the present invention.

FIG. 10 is a schematic view illustrating a case where carbon isexcessively supplied in Step 2 of the second sequence according to theembodiment of the present invention.

FIG. 11 is a schematic view illustrating a case where nitrogen isinsufficiently supplied in Step 3 of the second sequence according tothe embodiment of the present invention.

FIG. 12 is a schematic view illustrating formation of a silicon boroncarbon nitride film on a wafer in the third sequence according to theembodiment of the present invention.

FIG. 13 is a schematic view illustrating a case where carbon isexcessively supplied in Step 2 of the third sequence according to theembodiment of the present invention.

FIG. 14 is a schematic view illustrating a case where nitrogen isinsufficiently supplied in Step 4 of the third sequence according to theembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described hereinafter withreference to the attached drawings.

FIG. 1 is a vertical sectional view schematically illustrating avertical process furnace 202 of a substrate processing apparatusaccording to a preferred embodiment of the present invention, and FIG. 2is a sectional view taken along line A-A of FIG. 1 for schematicallyillustrating the vertical process furnace 202 according to a preferredembodiment of the present invention.

As shown in FIG. 1, the process furnace 202 includes a heater 207 usedas a heating unit (heating mechanism). The heater 207 has a cylindricalshape and is vertically installed in a state where the heater 207 issupported on a heater base (not shown) which is a holding plate. Asdescribed later, the heater 207 is also used as an activation mechanismfor activating gas by heat.

Inside the heater 207, a reaction tube 203 constituting a reactionvessel (process vessel) is installed concentrically with the heater 207.The reaction tube 203 is made of a heat-resistant material such as aquartz (SiO₂) or silicon carbide (SiC) and has a cylindrical shape witha closed top side and an opened bottom side. The hollow part of thereaction tube 203 forms a process chamber 201 and is configured toaccommodate substrates such as wafers 200 by using a boat 217 (describedlater) in a manner such that the wafers 200 are horizontally positionedand vertically arranged in multiple stages.

At the lower part of the reaction tube 203 in the process chamber 201, afirst nozzle 249 a, a second nozzle 249 b, a third nozzle 249 c, and afourth nozzle 249 d are installed through the reaction tube 203. A firstgas supply pipe 232 a, a second gas supply pipe 232 b, a third gassupply pipe 232 c, and a fourth gas supply pipe 232 d are connected tothe first nozzle 249 a, the second nozzle 249 b, the third nozzle 249 c,and the fourth nozzle 249 d, respectively. In this way, at the reactiontube 203, four nozzles 249 a, 249 b, 249 c, and 249 d, and four gassupply pipes 232 a, 232 b, 232 c, and 232 d are installed, and it isconfigured such that a plurality of kinds of gases, here, four kinds ofgases, can be supplied to the reaction tube 203.

At the first gas supply pipe 232 a, a flowrate controller (flowratecontrol unit) such as a mass flow controller (MFC) 241 a, and an on-offvalve such as a valve 243 a are sequentially installed from the upstreamside of the first gas supply pipe 232 a. In addition, a first inert gassupply pipe 232 e is connected to the downstream side of the valve 243 aof the first gas supply pipe 232 a. At the first inert gas supply pipe232 e, a flowrate controller (flowrate control unit) such as an MFC 241e, and an on-off valve such as a valve 243 e are sequentially installedfrom the upstream side of the first inert gas supply pipe 232 e. Inaddition, the first nozzle 249 a is connected to the leading end of thefirst gas supply pipe 232 a. In an arc-shaped space between the innerwall of the reaction tube 203 and wafers 200, the first nozzle 249 a iserected in a manner such that the first nozzle 249 a extends upward fromthe lower side to the upper side along the inner wall of the reactiontube 203 in a direction in which the wafers 200 are stacked. The firstnozzle 249 a is an L-shaped long nozzle. Gas supply holes 250 a areformed through the lateral surface of the first nozzle 249 a. The gassupply holes 250 a are opened toward the centerline of the reaction tube203. The gas supply holes 250 a are formed at a plurality of positionsalong the lower side to the upper side of the reaction tube 203, and thegas supply holes 250 a have the same size and are arranged at the samepitch. A first gas supply system is constituted mainly by the first gassupply pipe 232 a, the MFC 241 a, the valve 243 a, and the first nozzle249 a. In addition, a first inert gas supply system is constitutedmainly by the first inert gas supply pipe 232 e, the MFC 241 e, and thevalve 243 e.

At the second gas supply pipe 232 b, a flowrate controller (flowratecontrol unit) such as a mass flow controller (MFC) 241 b, and an on-offvalve such as a valve 243 b are sequentially installed from the upstreamside of the second gas supply pipe 232 b. In addition, a second inertgas supply pipe 232 f is connected to the downstream side of the valve243 b of the second gas supply pipe 232 b. At the second inert gassupply pipe 232 f, a flowrate controller (flowrate control unit) such asan MFC 241 f, and an on-off valve such as a valve 243 f are sequentiallyinstalled from the upstream side of the second inert gas supply pipe 232e. In addition, the second nozzle 249 b is connected to the leading endof the second gas supply pipe 232 b. In an arc-shaped space between theinner wall of the reaction tube 203 and wafers 200, the second nozzle249 b is erected in a manner such that the second nozzle 249 b extendsupward from the lower side to the upper side along the inner wall of thereaction tube 203 in a direction in which the wafers 200 are stacked.The second nozzle 249 b is an L-shaped long nozzle. Gas supply holes 250b are formed through the lateral surface of the second nozzle 249 a. Thegas supply holes 250 b are opened toward the centerline of the reactiontube 203. The gas supply holes 250 b are formed at a plurality ofpositions along the lower side to the upper side of the reaction tube203, and the gas supply holes 250 b have the same size and are arrangedat the same pitch. A second gas supply system is constituted mainly bythe second gas supply pipe 232 b, the MFC 241 b, the valve 243 b, andthe second nozzle 249 b. In addition, a second inert gas supply systemis constituted mainly by the second inert gas supply pipe 232 f, the MFC241 f, and the valve 243 f.

At the third gas supply pipe 232 c, a flowrate controller (flowratecontrol unit) such as a mass flow controller (MFC) 241 c, and an on-offvalve such as a valve 243 c are sequentially installed from the upstreamside of the third gas supply pipe 232 c. In addition, a third inert gassupply pipe 232 g is connected to the downstream side of the valve 243 cof the third gas supply pipe 232 c. At the third inert gas supply pipe232 g, a flowrate controller (flowrate control unit) such as an MFC 241g, and an on-off valve such as a valve 243 g are sequentially installedfrom the upstream side of the third inert gas supply pipe 232 g. Inaddition, the third nozzle 249 c is connected to the leading end of thethird gas supply pipe 232 c. In an arc-shaped space between the innerwall of the reaction tube 203 and wafers 200, the third nozzle 249 c iserected in a manner such that the third nozzle 249 c extends upward fromthe lower side to the upper side along the inner wall of the reactiontube 203 in a direction in which the wafers 200 are stacked. The thirdnozzle 249 c is an L-shaped long nozzle. Gas supply holes 250 c areformed through the lateral surface of the third nozzle 249 c. The gassupply holes 250 c are opened toward the centerline of the reaction tube203. The gas supply holes 250 c are formed at a plurality of positionsalong the lower side to the upper side of the reaction tube 203, and thegas supply holes 250 c have the same size and are arranged at the samepitch. A third gas supply system is constituted mainly by the third gassupply pipe 232 c, the MFC 241 c, the valve 243 c, and the third nozzle249 c. In addition, a third inert gas supply system is constitutedmainly by the third inert gas supply pipe 232 g, the MFC 241 g, and thevalve 243 g.

At the fourth gas supply pipe 232 d, a flowrate controller (flowratecontrol unit) such as an MFC 241 d, and an on-off valve such as a valve243 d are sequentially installed from the upstream side of the fourthgas supply pipe 232 d. In addition, a fourth inert gas supply pipe 232 his connected to the downstream side of the valve 243 d of the fourth gassupply pipe 232 d. At the fourth inert gas supply pipe 232 h, a flowratecontroller (flowrate control unit) such as an MFC 241 h, and an on-offvalve such as a valve 243 h are sequentially installed from the upstreamside of the fourth inert gas supply pipe 232 h. The fourth nozzle 249 dis connected to the leading end of the fourth gas supply pipe 232 d. Thefourth nozzle 249 d is installed in a buffer chamber 237 forming a gasdiffusion space.

The buffer chamber 237 is installed in an arc-shaped space between thereaction tube 203 and wafers 200 in a manner such that the bufferchamber 237 is located from the lower side to the upper side of theinner wall of the reaction tube 203 in a direction in which the wafers200 are stacked. At an end of a wall of the buffer chamber 237 adjacentto the wafers 200, gas supply holes 250 e are formed to supply gastherethrough. The gas supply holes 250 e are opened toward thecenterline of the reaction tube 203. The gas supply holes 250 e areformed at a plurality of positions along the lower side to the upperside of the reaction tube 203, and the gas supply holes 250 e have thesame size and are arranged at the same pitch.

The fourth nozzle 249 d is installed in the buffer chamber 237 at an endopposite to the end where the gas supply holes 250 e are formed, in amanner such that the first nozzle 249 a is erected upward along thelower side to the upper side of the inner wall of the reaction tube 203in a direction in which the wafers 200 are stacked. The fourth nozzle249 d is an L-shaped long nozzle. Gas supply holes 250 d are formedthrough the lateral surface of the fourth nozzle 249 d. The gas supplyholes 250 d are opened toward the centerline of the buffer chamber 237.Like the gas supply holes 250 e of the buffer chamber 237, the gassupply holes 250 d are formed at a plurality of positions along thelower side to the upper side of the reaction tube 203. If there is asmall pressure difference between the inside of the buffer chamber 237and the inside of the process chamber 201, it may be configured suchthat the gas supply holes 250 d have the same size and are arranged atthe same pitch from the upstream side (lower side) to the downstreamside (upper side); however if the pressure difference is large, it maybe configured such that the size of the gas supply holes 250 d increasesor the pitch of the gas supply holes 250 d decreases as it goes from theupstream side to the downstream side.

In the current embodiment, since the size or pitch of the gas supplyholes 250 d of the fourth nozzle 249 d is adjusted from the upstreamside to the downstream side as described above, although the velocitiesof gas streams injected through the gas supply holes 250 d aredifferent, the flowrates of the gas streams injected through the gassupply holes 250 d can be approximately equal. Gas streams injectedthrough the respective gas supply holes 250 d are first introduced intothe buffer chamber 237 so as to reduce the velocity difference of thegas streams.

That is, gas injected into the buffer chamber 237 through the gas supplyholes 250 d of the fourth nozzle 249 d is reduced in particle velocityand is then injected from the buffer chamber 237 to the inside of theprocess chamber 201 through the gas supply holes 250 e of the bufferchamber 237. Owing to this structure, when gas injected into the bufferchamber 237 through the gas supply holes 250 d of the fourth nozzle 249d is injected into the process chamber 201 through the gas supply holes250 e of the buffer chamber 237, the flowrate and velocity of the gascan be uniform.

A fourth gas supply system is constituted mainly by the fourth gassupply pipe 232 d, the MFC 241 d, the valve 243 d, the fourth nozzle 249d, and the buffer chamber 237. In addition, a fourth inert gas supplysystem is constituted mainly by the fourth inert gas supply pipe 232 h,the MFC 241 h, and the on-off valve 243 h.

For example, silicon source gas, that is, gas containing silicon (Si)(Silicon-containing gas) is supplied from the first gas supply pipe 232a to the inside of the process chamber 201 through the MFC 241 a, thevalve 243 a, and the first nozzle 249 a. For example, dichlorosilane(SiH₂Cl₂, DCS) gas may be used as silicon-containing gas.

For example, gas containing carbon (C) (carbon-containing gas) issupplied from the second gas supply pipe 232 b to the inside of theprocess chamber 201 through the MFC 241 b, the valve 243 b, and thesecond nozzle 249 b. For example, propylene (C₃H₆) gas may be used ascarbon-containing gas. In addition, gas containing hydrogen (H)(H-containing gas) may be supplied from the second gas supply pipe 232 bto the inside of the process chamber 201 through the MFC 241 b, thevalve 243 b, and the second nozzle 249 b. For example, hydrogen (H₂) gasmay be used as hydrogen-containing gas.

For example, gas containing boron (B) (boron-containing gas) is suppliedfrom the third gas supply pipe 232 c to the inside of the processchamber 201 through the MFC 241 c, the valve 243 c, and the third nozzle249 c. For example, boron trichloride (BCl₃) gas may be used asboron-containing gas. In addition, gas containing oxygen (O)(oxygen-containing gas) may be supplied from the third gas supply pipe232 c to the inside of the process chamber 201 through the MFC 241 c,the valve 243 c, and the third nozzle 249 c. For example, oxygen (O₂)gas or nitrous oxide (N₂O) may be used as oxygen-containing gas.

For example, gas containing nitrogen (N) (nitrogen-containing gas) issupplied from the fourth gas supply pipe 232 d to the inside of theprocess chamber 201 through the MFC 241 d, the valve 243 d, the fourthnozzle 249 d, and the buffer chamber 237. For example, ammonia (NH₃) gasmay be used as nitrogen-containing gas.

For example, nitrogen (N₂) gas is supplied to the inside of the processchamber 201 from the inert gas supply pipes 232 e, 232 f, 232 g, and 232h through the MFCs 241 e, 241 f, 241 g, and 241 h, the valves 243 e, 243f, 243 g, and 243 h, and the gas supply pipes 232 a, 232 b, 232 c, and232 d, the gas nozzles 249 a, 249 b, 249 c, and 249 d, and the bufferchamber 237.

In the case where gases are supplied from the gas supply pipes, forexample, as described above, the first gas supply system constitutes asource gas supply system, that is, a silicon-containing gas supplysystem (silane-based gas supply system). In addition, the second gassupply system constitutes a carbon-containing or hydrogen-containing gassupply system. In addition, the third gas supply system constitutes aboron-containing or oxygen-containing gas supply system. In addition,the fourth gas supply system constitutes a nitrogen-containing gassupply system.

Inside the buffer chamber 237, as shown in FIG. 2, a first rod-shapedelectrode 269 which is a first electrode having a long slender shape,and a second rod-shaped electrode which is a second electrode having along slender shape are installed in a manner such that the first andsecond rod-shaped electrodes 269 and 270 extend from the lower side tothe upper side of the reaction tube 203 in a direction in which wafers200 are stacked. Each of the first and second rod-shaped electrodes 269and 270 is parallel with the fourth nozzle 249 d. The first and secondrod-shaped electrodes 269 and 270 are respectively protected byelectrode protection pipes 275 which cover the first and secondrod-shaped electrodes 269 and 270 from the upper parts to the lowerparts thereof. One of the first and second rod-shaped electrodes 269 and270 is connected to a high-frequency power source 273 through a matchingdevice 272, and the other is grounded to the earth (referencepotential). Therefore, plasma can be generated in a plasma generationregion between the first and second rod-shaped electrodes 269 and 270. Aplasma source, which is a plasma generator (plasma generating unit), isconstituted mainly by the first rod-shaped electrode 269, the secondrod-shaped electrode 270, the electrode protection pipes 275, thematching device 272, and the high-frequency power source 273. The plasmasource is used as an activation mechanism for activating gas by usingplasma.

The electrode protection pipes 275 are configured such that the firstand second rod-shaped electrodes 269 and 270 can be respectivelyinserted into the buffer chamber 237 in a state where the first andsecond rod-shaped electrodes 269 and 270 are isolated from theatmosphere of the buffer chamber 237. If the insides of the electrodeprotection pipes 275 have the same atmosphere as the outside air, thefirst and second rod-shaped electrodes 269 and 270 that are respectivelyinserted in the electrode protection pipes 275 may be oxidized due toheat emitted from the heater 207. Therefore, an inert gas purgemechanism is installed to prevent oxidation of the first rod-shapedelectrode 269 or the second rod-shaped electrode 270 by filling orpurging the insides of the electrode protection pipes 275 with inert gassuch as nitrogen to maintain the oxygen concentration of the insides ofthe electrode protection pipes 275 at a sufficiently low level.

At the reaction tube 203, an exhaust pipe 231 is installed to exhaustthe inside atmosphere of the process chamber 201. A vacuum exhaustdevice such a vacuum pump 246 is connected to the exhaust pipe 231through a pressure detector (pressure detecting unit) such as a pressuresensor 245 configured to detect the inside pressure of the processchamber 201 and a pressure regulator (pressure regulating unit) such asan auto pressure controller (APC) valve 244, so that the inside of theprocess chamber 201 can be vacuum-evacuated to a predetermined pressure(vacuum degree). The APC valve 244 is an on-off valve, which can beopened and closed to start and stop vacuum evacuation of the inside ofthe process chamber 201 and can be adjusted in degree of valve openingfor pressure adjustment. Mainly, the exhaust pipe 231, the APC valve244, the vacuum pump 246, and the pressure sensor 245 constitute anexhaust system.

At the lower side of the reaction tube 203, a seal cap 219 is installedas a furnace port cover capable of hermetically closing the openedbottom side of the reaction tube 203. The seal cap 219 is configured tomake contact with the bottom side of the reaction tube 203 in aperpendicular direction from the lower side. For example, the seal cap219 is made of a metal such as stainless steel and has a disk shape. Onthe surface of the seal cap 219, an O-ring 220 is installed as a sealmember configured to make contact with the bottom side of the reactiontube 203. At a side of the seal cap 219 opposite to the process chamber201, a rotary mechanism 267 is installed to rotate the boat 217. Arotation shaft 255 of the rotary mechanism 267 is connected to the boat217 (described later) through the seal cap 219, so as to rotate wafers200 by rotating the boat 217. The seal cap 219 is configured to bevertically moved by an elevator such as a boat elevator 115 verticallyinstalled outside the reaction tube 203, so that the boat 217 can beloaded into and unloaded from the process chamber 201.

The boat 217, which is a substrate support tool, is made of aheat-resistant material such as quartz or silicon carbide and isconfigured to support a plurality of wafers 200 in a state where thewafers 200 are horizontally oriented and arranged in multiple stageswith the centers of the wafers 200 being aligned with each other. At thelower part of the boat 217, an insulating member 218 made of aheat-resistant material such as quartz or silicon carbide is installedso as to prevent heat transfer from the heater 207 to the seal cap 219.The insulating member 218 may include a plurality of insulating platesmade of a heat-resistant material such as quartz or silicon carbide, andan insulating plate holder configured to support the insulating platesin a state where the insulating plates are horizontally oriented andarranged in multiple stages.

Inside the reaction tube 203, a temperature sensor 263 is installed as atemperature detector, and by controlling power supplied to the heater207 based on temperature information detected by the temperature sensor263, desired temperature distribution can be attained at the inside ofthe process chamber 201. Like the nozzles 249 a, 249 b, 249 c, and 249d, the temperature sensor 263 has an L-shape and is installed along theinner wall of the reaction tube 203.

A controller 121, which is a control unit (control device), is connectedto devices such as the MFCs 241 a, 241 b, 241 c, 241 d, 241 e, 241 f,241 g, and 241 h; valves 243 a, 243 b, 243 c, 243 d, 243 e, 243 f, 243g, and 243 h; the pressure sensor 245; the APC valve 244; the vacuumpump 246; the heater 207; the temperature sensor 263; the boat rotarymechanism 267; the boat elevator 115; the high-frequency power source273; and the matching device 272. The controller 121 controls, forexample, flowrates of various gases by using the MFCs 241 a, 241 b, 241c, 241 d, 241 e, 241 f, 241 g, and 241 h; opening/closing operations ofvalves 243 a, 243 b, 243 c, 243 d, 243 e, 243 f, 243 g, and 243 h;opening/closing operations of the APC valve 244 and pressure adjustingoperations of the APC valve 244 based on the pressure sensor 245; thetemperature of the heater 207 based on the temperature sensor 263;starting/stopping operations of the vacuum pump 246; the rotation speedof the boat rotary mechanism 267; elevating operations of the boatelevator 115; power supply to the high-frequency power source 273; andimpedance adjusting operations using the matching device 272.

Next, explanations will be given on three exemplary sequences (a firstsequence, a second sequence, and a third sequence) for a process offorming an insulating film on a substrate, which is one of a pluralityof processes for manufacturing a semiconductor device by using theabove-described process furnace of the substrate processing apparatus.In the following descriptions, parts of the substrate processingapparatus are controlled by the controller 121.

In a conventional chemical vapor deposition (CVD) method or atomic layerdeposition (ALD) method, for example, in a CVD method, a plurality ofkinds of gases containing a plurality of elements that constitute a filmto be formed are simultaneously supplied, and in an ALD method, aplurality of kinds of gases containing a plurality of elements thatconstitute a film to be formed are alternately supplied. Then, a SiO₂film or a Si₃N₄ film is formed by controlling supply conditions such asthe flowrates of the supply gases, the supply times of the supply gases,and plasma power. In such a technique, for example, in the case offorming a SiO₂ film, supply conditions are controlled so as to adjustthe composition ratio of the SiO₂ film to the stoichiometric compositionof O/Si÷2, and in the case of forming a Si₃N₄ film, supply conditionsare controlled so as to adjust the composition ratio of the Si₃N₄ filmto the stoichiometric composition of N/Si÷1.33.

However, according to an embodiment of the present invention, supplyconditions are controlled so that the composition ratio of a film to beformed can be different from the stoichiometric composition. That is,supply conditions are controlled so that at least one of a plurality ofelements constituting a film can be excessive in amount as compared withother elements in terms of the stoichiometric composition. Hereinafter,exemplary sequences for a process of forming a film while controllingthe ratio of a plurality of elements constituting the film, that is, thecomposition ratio of the film, will be explained.

(First Sequence)

In the first place, a first sequence will now be described according toan embodiment. FIG. 3 is a view illustrating gas supply timing andplasma power supply timing in the first sequence of the currentembodiment; FIG. 6 is a schematic view illustrating formation of asilicon nitride film on a wafer according to the first sequence of thecurrent embodiment; FIG. 7 is a schematic view illustrating a case wheresilicon is excessively supplied in Step 1 of the first sequenceaccording to the current embodiment; and FIG. 8 is a schematic viewillustrating a case where nitrogen is insufficiently supplied in Step 2of the first sequence according to the current embodiment.

The first sequence of the current embodiment includes a process offorming a first layer including a first element on a wafer 200 bysupplying a gas containing the first element (a first element-containinggas) to the inside of a process vessel in which the wafer 200 isaccommodated; and

a process of forming a second layer including the first element and asecond element by supplying a gas containing the second element (asecond element-containing gas) to the inside of the process vessel tomodify the first layer,

wherein the process of forming the first layer and the process offorming the second layer are set to one cycle, and the cycle is repeatedat least once so as to form a thin film including the first and secondelements and having a predetermined thickness.

In the first sequence, the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in one process of the process of forming of the firstlayer and the process of forming of the second layer are controlled tobe higher or longer than the pressure of the inside of the processvessel, or the pressure of the inside of the process vessel and the timeof supplying the gas in the one process when the thin film having astoichiometric composition is formed.

Alternatively, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the other process of the process of forming the first layerand the process of forming the second layer are controlled to be loweror shorter than the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the other process when the thin film having thestoichiometric composition is formed.

In this way, one of the elements of the thin film can be excessive ascompared with the other in terms of the stoichiometric composition.

The process of forming the first layer is performed under a conditionwhere a CVD reaction is caused. In the process, a first element layerincluding less than one atomic layer to several atomic layers of thefirst element is formed on the wafer 200 as the first layer. The firstlayer may be a first element-containing gas adsorption layer.Preferably, the first element may be an element that can turn into solidby itself. The first element layer is a general term for a layer made ofthe first element, such as a continuous layer, a discontinuous layer,and a thin film in which such layers are overlapped. In addition, acontinuous layer formed of the first element may also be called “a thinfilm.” In addition, the first element-containing gas adsorption layer isa term including a continuous chemical adsorption layer and adiscontinuous chemical adsorption layer that are formed of molecules ofthe first element-containing gas. Furthermore, the expression “a layerless than one atomic layer” is used to denote a discontinuous atomiclayer. In a condition where the first element-containing gas decomposesby itself, the first element layer is formed by deposition of the firstelement on the wafer 200. In a condition where the firstelement-containing gas does not decompose by itself, a firstelement-containing gas adsorption layer is formed by adsorption of thefirst element-containing gas on the wafer 200. The former case where thefirst element layer is formed on the wafer 200 is more preferable thanthe latter case where the first element-containing gas adsorption layeris formed on the wafer 200 because the film forming rate of the formercase is higher than that of the latter case.

In the process of forming the second layer, the secondelement-containing gas is activated by plasma or heat and supplied tothe first layer to cause a part of the first layer to react with thesecond element-containing gas for modifying the first layer and thusforming the second layer including the first and second elements. Forexample, if several atomic layers of the first element are formed as thefirst layer in the process of forming the first layer, the surfaceatomic layer of the several atomic layers may partially or entirely beallowed to react with the second element-containing gas. Alternatively,the surface atomic layer and the next lower atomic layers among theseveral atomic layers of the first layer formed of the first element maybe allowed to react with the second element-containing gas. However, inthe case where the first layer is constituted by the several atomiclayers including the first element, it may be preferable that only thesurface atomic layer of the first layer be modified because thecomposition ratio of the thin film can be controlled more easily.Preferably, the second element may be an element that cannot turn intosolid by itself. The second element-containing gas may be supplied afterbeing activated by plasma or heat. FIG. 3 illustrates an example wherethe second element-containing gas is supplied after being activated byplasma. If the second element-containing gas is supplied after beingactivated by heat, soft reaction can be caused for soft modification.

For example, in the case where the composition ratio of the thin film iscontrolled in a manner such that the first element is excessive ascompared with the second element in terms of the stoichiometriccomposition, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming the first layer are controlled to behigher or longer than the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in the process of forming the first layer when thethin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the first element can be excessively supplied in theprocess of forming the first layer. Therefore, owing to the excessivesupply of the first element in the process of forming the first layer,the modification reaction of the first layer is not saturated in theprocess of forming the second layer. That is, as compared with the casewhere the thin film is formed to have the stoichiometric composition, anexcessive number of atoms of the first element are supplied in theprocess of forming the first layer, and thus, in the process of formingthe second layer, the modification reaction of the first layer can berestricted.

Alternatively, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming the second layer are controlled to belower or shorter than the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in the process of forming the second layer when thethin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the second element can be insufficiently supplied in theprocess of forming the second layer. Therefore, owing to theinsufficient supply of the second element in the process of forming thesecond layer, the modification reaction of the first layer is notsaturated in the process of forming the second layer. That is, ascompared with the case where the thin film is formed to have thestoichiometric composition, an insufficient number of atoms of thesecond element are supplied in the process of forming the second layer,and thus, in the process of forming the second layer, the modificationreaction of the first layer can be restricted.

For example, like the O/Si ratio of a SiO₂ film or the N/Si ratio of aSi₃N₄ film, in the case where the portion of O or N being the secondelement is relatively great in the saturated bonding ratio, as describedabove, it is controlled such that modification reaction is not saturatedin the process of forming the second layer.

Hereinafter, the first sequence of the current embodiment will beexplained more specifically. In the following description, anexplanation will be given on an example where a silicon nitride (SiN)film is formed on a substrate as an insulating film according to thesequence shown in FIG. 3 under the conditions where silicon (Si) is thefirst element, nitrogen (N) is the second element, DCS gas which is asilicon-containing gas is used as the first element-containing gas, andNH₃ gas which is a nitrogen-containing gas is used as the secondelement-containing gas. Furthermore, in the following description of theexample, the composition ratio of the silicon nitride film is controlledsuch that silicon (Si) is excessive as compared with nitrogen (N) interms of the stoichiometric composition. In addition, in the example,the first gas supply system constitutes a silicon-containing gas supplysystem (first element-containing gas supply system), and the fourth gassupply system constitutes a nitrogen-containing gas supply system(second element-containing gas supply system).

After a plurality of wafers 200 are charged into the boat 217 (wafercharging), as shown in FIG. 1, the boat 217 in which the plurality ofwafers 200 are supported is lifted and loaded into the process chamber201 by the boat elevator 115 (boat loading). In this state, the bottomside of the reaction tube 203 is sealed by the seal cap 219 with theO-ring 220 being disposed therebetween.

The inside of the process chamber 201 is vacuum-evacuated to a desiredpressure (vacuum degree) by using the vacuum pump 246. At this time, thepressure inside the process chamber 201 is measured by the pressuresensor 245, and based on the measured pressure, the APC valve 244 isfeedback-controlled (pressure adjustment). In addition, the inside ofthe process chamber 201 is heated to a desired temperature by using theheater 207. At this time, to obtain desired temperature distributioninside the process chamber 201, power to the heater 207 isfeedback-controlled based on temperature information measured by thetemperature sensor 263 (temperature adjustment). Next, the boat 217 isrotated by the rotary mechanism 267 to rotate the wafers 200 (waferrotation). Thereafter, the following two steps are sequentiallyperformed.

[Step 1]

The valve 243 a of the first gas supply pipe 232 a is opened to allow aflow of DCS gas. The flowrate of the DCS gas flowing through the firstgas supply pipe 232 a is controlled by the MFC 241 a. Then, the DCS gasis supplied to the inside of the process chamber 201 through the gassupply holes 250 a of the first nozzle 249 a and is exhausted throughthe exhaust pipe 231. At the time, the valve 243 e is also opened sothat inert gas such as N₂ gas can flow through the inert gas supply pipe232 e. The flow rate of N₂ gas flowing through the inert gas supply pipe232 e is controlled by the MFC 241 e. Then, together with the DCS gas,the N₂ gas is supplied to the inside of the process chamber 201 and isexhausted through the exhaust pipe 231.

At this time, the APC valve 244 is properly controlled to keep theinside pressure of the process chamber 201, for example, in the range of10 Pa to 1000 Pa. The flowrate of the DCS gas controlled by the MFC 241a is, for example, in the range of 10 sccm to 1000 sccm. The time duringwhich the wafers 200 are exposed to the DCS gas, that is, gas supplytime (exposing time) is in the range of, for example, 2 seconds to 120seconds. In addition, the temperature of the heater 207 is set to apredetermined temperature so that a CVD reaction can occur in theprocess chamber 201. That is, the temperature of the heater 207 is setsuch that the temperature of the wafers 200 can be in the range of, forexample, 300° C. to 650° C. If the temperature of the wafers 200 islower than 300° C., adsorption of DCS on the wafers 200 is difficult. Onthe other hand, if the temperature of the wafers 200 is higher than 650°C., uniformity can be easily broken due to strong CVD reaction.Therefore, it is preferable that the wafers 200 are kept in thetemperature range of 300° C. to 650° C.

By the supply of the DCS gas, a first layer including silicon as a firstelement is formed on an under-layer film of each of the wafers 200. Thatis, as shown in section (A) of FIG. 6, a silicon layer (Si layer) isformed on the wafer 200 (on the under-layer film of the wafer 200) as asilicon-containing layer constituted by less than one atomic layer toseveral atomic layers. The silicon-containing layer may be a DCSchemical adsorption layer. Silicon is an element that can turn intosolid by itself. The silicon layer is a general term for a layer made ofsilicon, such as a continuous layer, a discontinuous layer, and a thinfilm in which such layers are overlapped. In addition, a continuouslayer formed of silicon may also be called “a thin film.” In addition,the DCS chemical adsorption layer is a term including a continuouschemical adsorption layer of DCS molecules and a discontinuous chemicaladsorption layer of DCS molecules. If the thickness of thesilicon-containing layer formed on the wafer 200 is greater than thethickness of several atomic layers, nitridation effect cannot reach allover the silicon-containing layer in Step 2 (described later). Inaddition, the minimum of the silicon-containing layer that can be formedon the wafer 200 is less than one atomic layer. Therefore, preferably,the thickness of the silicon-containing layer ranges from the thicknessof less than one atomic layer to the thickness of several atomic layers.In a condition where the DCS gas decomposes by itself, the silicon layeris formed on the wafer 200 by deposition of silicon on the wafer 200,and in a condition where the DCS gas does not decompose by itself, a DCSchemical adsorption layer is formed by chemical adsorption of DCS on thewafer 200. The former case where the silicon layer is formed on thewafer 200 is more preferable than the latter case where the DCS chemicaladsorption layer is formed on the wafer 200 because the film formingrate of the former case is higher than that of the latter case.

After the silicon-containing layer is formed, the valve 243 a is closedto interrupt the supply of DCS gas. At this time, in a state where theAPC valve 244 of the exhaust pipe 231 is opened, the inside of theprocess chamber 201 is vacuum-evacuated by using the vacuum pump 246 sothat DCS gas remaining in the process chamber 201 without participatingin a reaction or after participating in the formation of thesilicon-containing layer can be removed from the inside of the processchamber 201. Furthermore, at this time, in a state where the valve 243 eis opened, supply of N₂ gas to the inside of the process chamber 201 iscontinued. Owing to this, DCS gas remaining in the process chamber 201without participating in a reaction or after participating in theformation of the silicon-containing layer can be removed from the insideof the process chamber 201 more effectively.

Instead of DCS gas, another gas can be alternatively used as thesilicon-containing gas. Examples of such alternative gases include: aninorganic source gas such as tetrachlorosilane (SiCl₄, abbreviation:TCS) gas, hexachlorodisilane (Si₂Cl₆, abbreviation: HCD) gas, andmonosilane (SiH₄) gas; and an organic source gas such asaminosilane-based gas such as tetrakisdimethylaminosilane(Si(N(CH₃)₂))₄, abbreviation: 4DMAS) gas, trisdimethylaminosilane(Si(N(CH₃)₂)₃H, abbreviation: 3DMAS) gas, bisdiethylaminosilane(Si(N(C₂H₅)₂)₂H₂, abbreviation: 2DEAS) gas, andbistertiarybutylaminosilane (SiH₂(NH(C₄H₉))₂, abbreviation: BTBAS) gas.Instead of N₂ gas, a rare gas such as Ar gas, He gas, Ne gas, and Xe gasmay be used as the inert gas.

[Step 2]

After removing gas remaining in the process chamber 201, the valve 243 dof the fourth gas supply pipe 232 d is opened to allow a flow of NH₃ gasthrough the fourth gas supply pipe 232 d. The flowrate of the NH₃ gasflowing through the fourth gas supply pipe 232 d is controlled by theMFC 241 d. Then, the NH₃ gas is supplied to the inside of the bufferchamber 237 through the gas supply holes 250 d of the fourth nozzle 249d. At this time, high-frequency power is applied across the firstrod-shaped electrode 269 and the second rod-shaped electrode 270 fromthe high-frequency power source 273 through the matching device 272, andthus the NH₃ gas supplied to the inside of the buffer chamber 237 isplasma-excited as an activated species and is supplied to the inside ofthe process chamber 201 through the gas supply holes 250 e while beingexhausted through the exhaust pipe 231. At this time, the valve 243 h isalso opened to allow a flow of N₂ gas through the inert gas supply pipe232 h. Then, together with the NH₃ gas, the N₂ gas is supplied to theinside of the process chamber 201 and is exhausted through the exhaustpipe 231.

When the NH₃ gas is plasma-excited as an activated species and isallowed to flow, the APC valve 244 is properly controlled so as toadjust the inside pressure of the process chamber 201, for example, inthe range of 10 Pa to 100 Pa. The flowrate of the NH₃ gas controlled bythe MFC 241 d is, for example, in the range of 100 sccm to 10000 sccm.The time during which the wafers 200 are exposed to the activatedspecies obtained by plasma-exciting the NH₃ gas, that is, gas supplytime (exposing time) is in the range of, for example, 2 seconds to 120seconds. At this time, like in Step 1, the temperature of the heater 207is set to a predetermined temperature so that the temperature of thewafers 200 can be in the range of, for example, 300° C. to 650° C. Inaddition, the high-frequency power applied across the first rod-shapedelectrode 269 and the second rod-shaped electrode 270 from thehigh-frequency power source 273 is set to be in the range of, forexample, 50 W to 1000 W. Since it is difficult to make the NH₃ gasreactive at the above-mentioned temperature range of the wafers 200 andthe pressure range of the inside of the process chamber 201 due to ahigh reaction temperature of the NH₃ gas, the NH₃ gas is plasma-excitedas an activated species and is then allowed to flow, and thus, thewafers 200 can be kept in the above-mentioned low temperature range.Alternatively, instead of plasma-exciting the NH₃ gas, the insidepressure of the process chamber 201 can be adjusted in the range of, forexample, 50 Pa to 3000 Pa by properly controlling the APC valve 244 soas to activate the NH₃ gas not by plasma but by heat. In the case wherethe NH₃ gas is supplied after being activated by heat, soft reaction canbe caused for soft nitriding (described later).

At this time, gas flowing in the process chamber 201 is either anactivated species obtained by plasma-exciting NH₃ gas orthermally-activated NH₃ gas obtained by keeping the inside of theprocess chamber 201 at a high pressure, that is, DCS gas does not flowin the process chamber 201. Therefore, the NH₃ gas does not cause avapor-phase reaction, but the NH₃ gas which is an activated species oris in an activated state is brought into reaction with a part of thesilicon-containing layer formed on the wafers 200 as a first layer inStep 1. As a result, the silicon-containing layer is nitrided andmodified into a second layer including silicon (first element) andnitrogen (second element), that is, into a silicon nitride (SiN) layer.

At this time, as shown in section (B) of FIG. 6, the nitriding reactionof the silicon-containing layer is not saturated. For example, in thecase where a silicon layer including several atomic layers is formed inStep 1, at least a part of the surface layer (the surface atomic layerof the atomic layers) is nitrided. That is, the surface layer ispartially or entirely nitrided. In this case, so as not to entirelynitride the silicon layer including several atomic layers, the siliconlayer is nitrided in a non-saturated condition. Alternatively, accordingto conditions, the surface atomic layer and the next lower atomic layersamong the several atomic layers of the silicon layer can be nitrided;however, the case where only the surface atomic layer is nitrided ispreferable because the composition ratio of the silicon nitride film canbe controlled more easily. In addition, for example, in the case where asilicon layer including one atomic layer or less than one atomic layeris formed in Step 1, a part of the silicon layer is nitrided. In thiscase, like in the above, so as not to entirely nitride the silicon layerincluding one atomic layer or less than one atomic layer, the siliconlayer is nitrided in a non-saturated condition. In addition, nitrogen isan element that cannot turn into solid by itself.

Thereafter, the valve 243 d of the fourth gas supply pipe 232 d isclosed to interrupt the supply of NH₃ gas. At this time, in a statewhere the APC valve 244 of the exhaust pipe 231 is opened, the inside ofthe process chamber 201 is vacuum-evacuated by using the vacuum pump 246so that NH₃ gas remaining in the process chamber 201 withoutparticipating in a reaction or after participating in the nitridingreaction can be removed from the inside of the process chamber 201.Furthermore, at this time, in a state where the valve 243 h is opened,supply of N₂ gas to the inside of the process chamber 201 is continued.Owing to this, NH₃ gas remaining in the process chamber 201 withoutparticipating in a reaction or after participating in the nitridingreaction can be removed from the inside of the process chamber 201 moreeffectively.

As a nitrogen-containing gas, not only NH₃ gas activated by plasma orheat, but also another gas such as N₂ gas, NF₃ gas, or N₃H₈ gasactivated by plasma or heat may be used; in addition, such a gas mayused after diluting the gas with a rare gas such as Ar gas, He gas, Negas, or Xe gas and activating the gas by plasma or heat.

By setting the above-described Step 1 and Step 2 to one cycle andrepeating this cycle at least once, a thin film includes silicon (firstelement) and nitrogen (second element), that is, a silicon nitride (SiN)film can be formed on each of the wafers 200 to a predeterminedthickness. Preferably, the cycle may be repeated a plurality of times.

In Step 1, the pressure of the inside of the process chamber 201, or thepressure of the inside of the process chamber 201 and the gas supplytime are controlled to be higher or longer than the pressure of theinside of the process chamber 201, or the pressure of the inside of theprocess chamber 201 and the gas supply time in Step 1 when the siliconnitride film having a stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the silicon nitride film is formed to have the stoichiometriccomposition, silicon can be excessively supplied in Step 1 (refer tosection (A) in FIG. 7). Therefore, owing to the excessive supply ofsilicon in Step 1, the nitriding reaction of the silicon-containinglayer is not saturated in Step 2 (refer to section (B) in FIG. 7). Thatis, as compared with the case where the silicon nitride film is formedto have the stoichiometric composition, an excessive number of siliconatoms are supplied in Step 1, and thus, in Step 2, the nitridingreaction of the silicon-containing layer can be restricted. Accordingly,the composition ratio of the silicon nitride (SiN) film can becontrolled in a manner such that silicon (Si) is excessive as comparewith nitrogen (N) in terms of the stoichiometric composition.

In the upper side of FIG. 7, schematic partial section views of a waferare shown to explain reaction states of steps during which a SiN film isformed to have a stoichiometric composition. In the lower side of FIG.7, schematic partial section views of a wafer are shown to explainreaction states of steps during which silicon (Si) is excessivelysupplied to form a SiN film having excessive silicon (Si) as comparedwith nitrogen (N) in terms of stoichiometric composition. Section (A)and section (B) of FIG. 7 illustrate reaction states of Step 1 and Step2, respectively. The upper side of FIG. 7 shows an exemplary case wherea continuous Si layer constituted by one atomic layer is formed in Step1 and the Si layer is entirely nitrided in Step 2, and the lower side ofFIG. 7 shows an exemplary case where a continuous Si layer constitutedby two atomic layers is formed in Step 1 and the surface atomic layer ofthe Si layer is nitrided in Step 2.

Alternatively, in Step 2, the pressure of the inside of the processchamber 201, or the pressure of the inside of the process chamber 201and the gas supply time are controlled to be lower or shorter than thepressure of the inside of the process chamber 201, or the pressure ofthe inside of the process chamber 201 and the gas supply time in Step 2when the silicon nitride having the stoichiometric composition isformed. By controlling the process conditions in this way, as comparedwith the case where the silicon nitride film is formed to have thestoichiometric composition, nitrogen can be insufficiently supplied inStep 2 (refer to section (B) in FIG. 8). Therefore, owing to theinsufficient supply of nitrogen in Step 2, the nitriding reaction of thesilicon-containing layer is not saturated in Step 2. That is, ascompared with the case where the silicon nitride film is formed to havethe stoichiometric composition, an insufficient number of nitrogen atomsare supplied in Step 2, and thus, in Step 2, the nitriding reaction ofthe silicon-containing layer can be restricted. Accordingly, thecomposition ratio of the silicon nitride (SiN) film can be controlled ina manner such that silicon (Si) is excessive as compare with nitrogen(N) in terms of the stoichiometric composition.

In the upper side of FIG. 8, schematic partial section views of a waferare shown to explain reaction states of steps during which a SiN film isformed to have a stoichiometric composition. In the lower side of FIG.8, schematic partial section views of a wafer are shown to explainreaction states of steps during which nitrogen (N) is insufficientlysupplied to form a SiN film having excessive silicon (Si) as comparedwith nitrogen (N) in terms of stoichiometric composition. Section (A)and section (B) of FIG. 8 illustrate reaction states of Step 1 and Step2, respectively. The upper side of FIG. 8 shows an exemplary case wherea continuous Si layer constituted by one atomic layer is formed in Step1 and the Si layer is entirely nitrided in Step 2, and the lower side ofFIG. 8 shows an exemplary case where a continuous Si layer constitutedby one atomic layer is formed in Step 1 and the surface of the Si layeris partially nitrided in Step 2.

After a silicon nitride film having a predetermined composition andthickness is formed in the film-forming process, inert gas such as N₂gas is supplied to the inside of the process chamber 201 and isexhausted from the inside of the process chamber 201 so as to purge theinside of the process chamber 201 (gas purge). Then, the insideatmosphere of the process chamber 201 is replaced with inert gas(replacement with inert gas), and the inside of the process chamber 201returns to atmospheric pressure (return to atmospheric pressure).

Thereafter, the seal cap 219 is moved downward by the boat elevator 115so as to open the bottom side of the reaction tube 203 and unload theboat 217 in which the processed wafers 200 are supported from the insideof the reaction tube 203 through the bottom side of the reaction tube203 (boat unloading). After that, the processed wafers 200 aredischarged from the boat 217 (wafer discharging).

In the above-described example of the first sequence of the currentembodiment, a silicon-containing gas and a nitrogen-containing gas arerespectively used as a first element-containing gas and a secondelement-containing gas so as to form a SiN film; however, the presentinvention is not limited to the example but various changes andmodifications can be made within the scope and spirit of the presentinvention.

For example, an aluminum-containing gas and a nitrogen-containing gasmay be used as a first element-containing gas and a secondelement-containing gas, respectively, so as to form an aluminum nitride(AlN) film; a titanium-containing gas and a nitrogen-containing gas maybe used as a first element-containing gas and a secondelement-containing gas, respectively, so as to form a titanium nitride(TiN) film; or a boron-containing gas and a nitrogen-containing gas maybe used as a first element-containing gas and a secondelement-containing gas, respectively, so as to form a boron nitride (BN)film. In addition, for example, a silicon-containing gas and anoxygen-containing gas may be used as a first element-containing gas anda second element-containing gas, respectively, so as to form a siliconoxide (SiO) film; an aluminum-containing gas and an oxygen-containinggas may be used as a first element-containing gas and a secondelement-containing gas, respectively, so as to form an aluminum oxide(AlO) film; or a titanium-containing gas and an oxygen-containing gasmay be used as a first element-containing gas and a secondelement-containing gas, respectively, so as to form a titanium oxide(TiO) film. Furthermore, a silicon-containing gas and acarbon-containing gas may be used as a first element-containing gas anda second element-containing gas, respectively, so as to form a siliconcarbide (SiC) film.

As an aluminum-containing gas, for example, trimethylaluminum (Al(CH₃)₃,abbreviation: TMA) gas may be used. As a titanium-containing gas, forexample, titanium tetrachloride (TiCl₄) gas ortetrakis(dimethylamido)titanium (Ti[N(CH₃)₂]₄, abbreviation: TDMAT) gasmay be used. As a boron-containing gas, for example, boron trichloride(BCl₃) gas or diborane (B₂H₆) gas may be used. As a carbon-containinggas, for example, propylene (C₃H₆) gas or ethylene (C₂H₄) gas may beused. As an oxygen-containing gas, for example, oxygen (O₂) gas, ozone(O₃) gas, nitric oxide (NO) gas, nitrous oxide (N₂O), or vapor (H₂O) maybe used.

In the case where an oxygen-containing gas is used as a secondelement-containing gas, a hydrogen-containing gas can be suppliedtogether with the oxygen-containing gas. If an oxygen-containing gas anda hydrogen-containing gas are supplied to the inside of a process vesselkept at a pressure lower than atmospheric pressure (decompressed state),the oxygen-containing gas and the hydrogen-containing gas react witheach other to produce an oxidizing species containing oxygen (such asatomic oxygen) so that a first layer can be oxidized by the oxidizingspecies. In this case, oxidation can be performed with increasedoxidizing power as compared with the case of using an oxygen-containinggas only. This oxidizing treatment is performed under non-plasma anddecompressed state. As the hydrogen-containing gas, for example,hydrogen (H₂) gas may be used.

As explained above, according to the first sequence of the currentembodiment, a semiconductor element such as silicon (Si) or boron (B),or a metal element such as aluminum (Al) or titanium (Ti) may be used asa first element, and an element such as nitrogen (N), carbon (C), oroxygen (O) may be used as a second element.

(Second Sequence)

Next, a second sequence will now be described according to anembodiment.

FIG. 4 is a view illustrating gas supply timing in the second sequenceaccording to an embodiment of the present invention; FIG. 9 is aschematic view illustrating formation of a silicon carbonitride film ona wafer according to the second sequence of the embodiment of thepresent invention; FIG. 10 is a schematic view illustrating a case wherecarbon is excessively supplied in Step 2 of the second sequenceaccording to the embodiment of the present invention; and FIG. 11 is aschematic view illustrating a case where nitrogen is insufficientlysupplied in Step 3 of the second sequence according to the embodiment ofthe present invention. The second sequence of the current embodimentrelates to a method of controlling a composition ratio of threeelements.

The second sequence of the current embodiment includes a process offorming a first layer including a first element on a wafer 200 bysupplying a gas containing the first element (a first element-containinggas) to the inside of a process vessel in which the wafer 200 isaccommodated;

a process of forming a second layer including the first element and asecond element by supplying a gas containing the second element (secondelement-containing gas) to the inside of the process vessel, wherein thesecond layer is formed by forming a layer including the second elementon the first layer, or the second layer is formed by modifying the firstlayer; and

a process of forming a third layer including the first element, thesecond element, and a third element by supplying a gas containing thethird element (a third element-containing gas) to the inside of theprocess vessel to modify the second layer,

wherein the process of forming the first layer, the process of formingthe second layer, and the process of forming the third layer are set toone cycle, and the cycle is repeated at least once so as to form a thinfilm including the first to third elements and having a predeterminedthickness.

In the second sequence, the pressure of the inside of the processvessel, or the pressure of the inside of the process vessel and the timeof supplying the gas in one process of the process of forming of thefirst layer, the process of forming of the second layer, and the processof forming of the third layer are controlled to be higher or longer thanthe pressure of the inside of the process vessel, or the pressure of theinside of the process vessel and the time of supplying the gas in theone process when the thin film having a stoichiometric composition isformed.

Alternatively, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the other process of the process of forming of the firstlayer, the process of forming of the second layer, and the process offorming of the third layer are controlled to be lower or shorter thanthe pressure of the inside of the process vessel, or the pressure of theinside of the process vessel and the time of supplying the gas in theother process when the thin film having the stoichiometric compositionis formed.

In this way, one of the elements of the thin film can be excessive ascompared with the others in terms of the stoichiometric composition.

In the case of a thin film made of two elements (two-element thin film),the stoichiometric composition is unique. For example, thestoichiometric composition of a SiN film is unique, that is, Si:N=3:4.However, in the case of a three-element thin film, the stoichiometriccomposition is not unique unlike that of a two-element thin film but istwo or more. In the second sequence of the current embodiment, a thinfilm is formed in a manner such that the thin film has a compositionratio different from any of the stoichiometric compositions.

The process of forming the first layer is the same as the process offorming the first layer in the first sequence. That is, things regardingthe process of forming the first layer, such as process conditions,motivated reaction, layers, layer thickness, examples of the firstelement, examples of the first element-containing gas, and examples ofthe first layer, are the same as those regarding the process of formingthe first layer in the first sequence.

In the process of forming the second layer, the secondelement-containing gas is activated by plasma or heat and is thensupplied to the first layer, so that a layer including the secondelement and constituted by less than one to several atomic layers can beformed on the first layer or the first layer can be modified by reactionbetween a part of the first layer and the second element-containing gas.In this way, the second layer including the first and second elements isformed.

In the case where the second layer is formed by forming a layerincluding the second element on the first layer, the layer including thesecond element may be a second element layer or a secondelement-containing gas adsorption layer. The second element-containinggas adsorption layer includes an adsorption layer formed of a materialdecomposed from the second element-containing gas. The second elementlayer is a general term for a layer made of the second element, such asa continuous layer, a discontinuous layer, and a thin film in which suchlayers are overlapped. In addition, a continuous layer formed of thesecond element may also be called “a thin film.” In addition, the secondelement-containing gas adsorption layer is a term including a continuouschemical adsorption layer and a discontinuous chemical adsorption layerthat are formed of molecules of the second element-containing gas ormolecules of a material decomposed from the second element-containinggas. Preferably, the layer including the second element may be adiscontinuous chemical adsorption layer formed of molecules of thesecond element-containing gas or molecules of a material decomposed fromthe second element-containing gas, that is, the layer including thesecond element may be a chemical adsorption layer constituted by lessthan one atomic layer, so as to improve the controllability of thecomposition ratio of the thin film.

In the case where the second layer is formed by modifying the firstlayer, the first layer is modified by the same method as the method usedfor modifying the first layer in the process of forming the second layerin the first sequence.

The second element-containing gas may be supplied after being activatedby plasma or heat. FIG. 4 illustrates an example where the secondelement-containing gas is supplied after being activated by heat, thatis, an example for causing a soft reaction.

In the process of forming the third layer, the third element-containinggas is activated by plasma or heat and is then supplied to the secondlayer, so as to modify the second layer for forming the third layerincluding the first to third elements. For example, if the second layeris formed to have the first and second elements and be constituted byseveral atomic layers in the process of forming the second layer, thesurface atomic layer of the several atomic layers may partially orentirely be allowed to react with the third element-containing gas.Alternatively, the surface atomic layer and the next lower atomic layersamong the several atomic layers of the second layer formed of the firstand second elements may be allowed to react with the thirdelement-containing gas. However, in the case where the second layer isconstituted by the several atomic layers including the first and secondelements, it may be preferable that only the surface atomic layer of thesecond layer be modified because the composition ratio of the thin filmcan be controlled more easily. Preferably, the third element may be anelement that cannot turn into solid by itself. The thirdelement-containing gas may be supplied after being activated by plasmaor heat. FIG. 4 illustrates an example where the thirdelement-containing gas is supplied after being activated by heat, thatis, an example of causing a soft reaction for performing a softmodification.

A method such as a method of controlling the composition ratio of thethin film in a manner such that the first element is excessive ascompared with the second element in terms of the stoichiometriccomposition is the same as that used in the first sequence.

In the case where the composition ratio of the thin film is controlledin a manner such that the second element is excessive as compared withthe third element in terms of the stoichiometric composition or thethird element is excessive as compared with the second element in termsof the stoichiometric composition, the composition ratio is controlledbased on one of the two elements.

For example, in the case where the composition ratio of the thin film iscontrolled in a manner such that the second element is excessive ascompared with the third element in terms of the stoichiometriccomposition, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming the second layer are controlled to behigher or longer than the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in the process of forming the second layer when thethin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the second element can be excessively supplied in theprocess of forming the second layer. Therefore, owing to the excessivesupply of the second element in the process of forming the second layer,a region of the second layer that can be modified in the process offorming the third layer is reduced. That is, as compared with the casewhere the thin film is formed to have the stoichiometric composition, anexcessive number of atoms of the second element are supplied in theprocess of forming the second layer, and thus, in the process of formingthe third layer, the modification reaction of the second layer can berestricted.

Alternatively, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming of the third layer are controlled tobe lower or shorter than the pressure of the inside of the processvessel, or the pressure of the inside of the process vessel and the timeof supplying the gas in the process of forming the third layer when thethin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the third element can be insufficiently supplied in theprocess of forming the third layer. Therefore, owing to the insufficientsupply of the third element in the process of forming the third layer,the modification reaction of the second layer can be restricted in theprocess of forming the third layer. That is, as compared with the casewhere the thin film is formed to have the stoichiometric composition, aninsufficient number of atoms of the third element are supplied in theprocess of forming the third layer, and thus, in the process of formingthe third layer, the modification reaction of the second layer can berestricted.

In addition, for example, in the case where the composition ratio of thethin film is controlled in a manner such that the third element isexcessive as compared with the second element in terms of thestoichiometric composition, the pressure of the inside of the processvessel, or the pressure of the inside of the process vessel and the timeof supplying the gas in the process of forming the second layer arecontrolled to be lower or shorter than the pressure of the inside of theprocess vessel, or the pressure of the inside of the process vessel andthe time of supplying the gas in the process of forming the second layerwhen the thin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the second element can be insufficiently supplied in theprocess of forming the second layer. Therefore, owing to theinsufficient supply of the second element in the process of forming thesecond layer, a layer including the second element is formed in asmaller region or modification reaction of the first layer isrestricted. As a result, the third element becomes excessive as comparedwith the second element in terms of the stoichiometric composition.

If the second element is insufficiently supplied in the process offorming the second layer, a region of the second layer that can bemodified in the process of forming the third layer is increased. In thiscase, if the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming the third layer are controlled to behigher or longer than the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in the process of forming the third layer when thethin film having the stoichiometric composition is formed, the thirdelement can be excessively supplied in the process of forming the thirdlayer, and thus the third element can be controlled to be much excessiveas compared with the second element in terms of the stoichiometriccomposition. That is, by a combination of insufficient supply of thesecond element in the process of forming the second layer and excessivesupply of the third element in the process of forming the third layer,the modification reaction of the second layer can be facilitated in theprocess of forming the third layer, and thus the composition ratio ofthe thin film can be controlled in a manner such that the third elementis much excessive as compared with the second element in terms of thestoichiometric composition.

Hereinafter, the second sequence of the current embodiment will bedescribed more specifically. In the following description, anexplanation will be given on an example where a silicon carbonitride(SiCN) film is formed on a substrate as an insulating film according tothe sequence shown in FIG. 4 under the conditions where silicon (Si) isthe first element, carbon (C) is the second element, nitrogen (N) is thethird element, DCS gas which is a silicon-containing gas is used as thefirst element-containing gas, C₃H₆ gas which is a carbon-containing gasis used as the second element-containing gas, and NH₃ gas which is anitrogen-containing gas is used as the third element-containing gas.Furthermore, in the following description of the example, thecomposition ratio of the silicon carbonitride film is controlled suchthat carbon (C) is excessive as compared with nitrogen (N) in terms ofthe stoichiometric composition. In addition, in the example, the firstgas supply system constitutes a silicon-containing gas supply system(first element-containing gas supply system), the second gas supplysystem constitutes a carbon-containing gas supply system (secondelement-containing gas supply system), and the fourth gas supply systemconstitutes a nitrogen-containing gas supply system (thirdelement-containing gas supply system).

Wafer charging, boat loading, pressure adjustment, temperatureadjustment, and wafer rotation are performed in the same way as in thefirst sequence, and then, the following three steps are sequentiallyperformed.

[Step 1]

Step 1 is performed in the same way as Step 1 of the first sequence.That is, things regarding Step 1, such as process conditions, motivatedreaction, layers, layer thickness, examples of the first element,examples of the first element-containing gas, and examples of the firstlayer, are the same as those regarding Step 1 of the first sequence(refer to section (A) of FIG. 9).

[Step 2]

After completing Step 1 and removing gas remaining in the processchamber 201, the valve 243 b of the second gas supply pipe 232 b isopened to allow a flow of C₃H₆ gas through the second gas supply pipe232 b. The flowrate of the C₃H₆ gas flowing through the second gassupply pipe 232 b is controlled by the MFC 241 b. Then, the C₃H₆ gas issupplied to the inside of the process chamber 201 through the gas supplyholes 250 b of the second nozzle 249 b and is exhausted through theexhaust pipe 231. At this time, the valve 243 f is also opened to allowa flow of N₂ gas through the inert gas supply pipe 232 f. The N₂ gas issupplied to the inside of the process chamber 201 together with the C₃H₆gas and is exhausted through the exhaust pipe 231.

At this time, the APC valve 244 is properly controlled so as to adjustthe inside pressure of the process chamber 201, for example, in therange of 50 Pa to 3000 Pa. The flowrate of the C₃H₆ gas controlled bythe MFC 241 b is, for example, in the range of 100 sccm to 10000 sccm.The time during which wafers 200 are exposed to the C₃H₆ gas, that is,gas supply time (exposing time) is in the range of, for example, 2seconds to 120 seconds. At this time, like in Step 1, the temperature ofthe heater 207 is set to a predetermined temperature so that thetemperature of the wafers 200 can be in the range of, for example, 300°C. to 650° C. In the case where the C₃H₆ gas is activated by heat and issupplied, soft reaction can be caused, and thus a carbon-containinglayer can be easily formed (described later).

At this time, gas flowing in the process chamber 201 is C₃H₆ gasactivated by heat and DCS gas does not flow in the process chamber 201.Therefore, without causing a vapor-phase reaction, the C₃H₆ gas which isin an activated state is supplied to the wafers 200, and at this time,as shown in section (B) of FIG. 9, a carbon-containing layer constitutedby less than one atomic layer, that is, a discontinuouscarbon-containing layer, is formed on a silicon-containing layer formedin Step 1. In this way, a second layer including silicon (first element)and carbon (second element) is formed. In some cases, according toconditions, a part of the silicon-containing layer reacts with the C₃H₆gas, and as a result, the silicon-containing layer is modified(carbonized) to form a second layer including silicon and carbon.

The carbon-containing layer formed on the silicon-containing layer maybe a carbon layer (C-layer), a chemical adsorption layer of C₃H₆, or achemical adsorption layer of C_(x)H_(y) (a material decomposed fromC₃H₆). It is necessary that the carbon layer is a discontinuous layermade of carbon. In addition, it is necessary that the chemicaladsorption layer of C₃H₆ or C_(x)H_(y) is a discontinuous chemicaladsorption layer made of C₃H₆ or C_(x) H_(y). In the case where thecarbon-containing layer formed on the silicon-containing layer is acontinuous layer, for example, if adsorption of C_(x)H_(y) on thesilicon-containing layer is saturated and thus a continuous chemicaladsorption layer of C_(x)H_(y) is formed on the silicon-containinglayer, the entire surface of the silicon-containing layer is coveredwith the chemical adsorption layer of C_(x)H_(y). In this case, silicondoes not exist on the surface of the second layer, and thus it isdifficult to nitride the second layer in Step 3 (described later). Thereason for this is that nitrogen couples with silicon but does notcouple with carbon. So as to cause a desired nitriding reaction in Step3 (described later), adsorption of C_(x)H_(y) on the silicon-containinglayer should not be saturated so that silicon can be exposed on thesurface of the second layer.

Thereafter, the valve 243 b of the second gas supply pipe 232 b isclosed to interrupt supply of C₃H₆ gas. At this time, in a state wherethe APC valve 244 of the exhaust pipe 231 is opened, the inside of theprocess chamber 201 is vacuum-evacuated by using the vacuum pump 246 sothat C₃H₆ gas remaining in the process chamber 201 without participatingin a reaction or after participating in the formation of thecarbon-containing layer can be removed from the inside of the processchamber 201. Furthermore, at this time, in a state where the valve 243 fis opened, supply of N₂ gas to the inside of the process chamber 201 iscontinued. Owing to this, C₃H₆ gas remaining in the process chamber 201without participating in a reaction or after participating in theformation of the carbon-containing layer can be removed from the insideof the process chamber 201 more effectively.

As a carbon-containing gas, not only C₃H₆ gas, but also another gas suchas C₂H₄ gas may be used.

[Step 3]

After removing gas remaining in the process chamber 201, the valve 243 dof the fourth gas supply pipe 232 d is opened to allow a flow of NH₃ gasthrough the fourth gas supply pipe 232 d. The flowrate of the NH₃ gasflowing through the fourth gas supply pipe 232 d is controlled by theMFC 241 d. Then, the NH₃ gas is supplied to the inside of the bufferchamber 237 through the gas supply holes 250 d of the fourth nozzle 249d. At this time, high-frequency power is not applied across the firstrod-shaped electrode 269 and the second rod-shaped electrode 270. As aresult, the NH₃ gas supplied to the inside of the buffer chamber 237 isactivated by heat and is then supplied to the inside of the processchamber 201 through the gas supply holes 250 e while being exhaustedthrough the exhaust pipe 231. At this time, the valve 243 h is alsoopened to allow a flow of N₂ gas through the inert gas supply pipe 232h. Then, together with the NH₃ gas, the N₂ gas is supplied to the insideof the process chamber 201 and is exhausted through the exhaust pipe231.

When the NH₃ gas is activated by heat and is allowed to flow, the APCvalve 244 is properly controlled so as to adjust the inside pressure ofthe process chamber 201, for example, in the range of 50 Pa to 3000 Pa.The flowrate of the NH₃ gas controlled by the MFC 241 d is, for example,in the range of 100 sccm to 10000 sccm. The time during which the wafers200 are exposed to the NH₃ gas, that is, gas supply time (exposing time)is in the range of, for example, 2 seconds to 120 seconds. At this time,like in Step 1, the temperature of the heater 207 is set to apredetermined temperature so that the temperature of the wafers 200 canbe in the range of, for example, 300° C. to 650° C. Since it isdifficult to make the NH₃ gas reactive at the above-mentionedtemperature range of the wafers 200 due to a high reaction temperatureof the NH₃ gas, the process chamber 201 is kept at a relatively highpressure as mentioned above so as to activate the NH₃ gas by heat. Inthe case where the NH₃ gas is activated by heat and is supplied, softreaction can be caused for soft nitriding (described later).

At this time, gas flowing in the process chamber 201 isthermally-activated NH₃ gas, and neither DCS gas nor C₃H₆ gas flows inthe process chamber 201. Therefore, without causing a vapor-phasereaction, the activated NH₃ gas reacts with a part of the layerincluding silicon and carbon, that is, a part of the second layer formedon each of the wafers 200 in Step 2. As a result, the second layer isnitrided and modified into a third layer including silicon (firstelement), carbon (second element), and nitrogen (third element), thatis, into a silicon carbonitride (SiCN) layer.

At this time, as shown in section (C) of FIG. 9, the nitriding reactionof the second layer is not saturated. For example, in the case where asilicon layer constituted by several atomic layers is formed in Step 1and a carbon-containing layer constituted by less than one atomic layeris formed in Step 2, a part of the surface layer (the surface atomiclayer of the atomic layers) is nitrided. That is, a region (siliconexposed region) of the surface layer that can be nitrided is partiallyor entirely nitrided. In this case, so as not to entirely nitride thesecond layer, the nitriding of the second layer is performed under anon-saturated condition. Alternatively, according to conditions, thesurface atomic layer and the next lower atomic layers among the atomiclayers of the second layer can be nitrided; however, the case where onlythe surface atomic layer is nitrided is preferable because thecomposition ratio of the silicon carbonitride film can be controlledmore easily. In addition, for example, in the case where a silicon layerconstituted by one atomic layer or less than one atomic layer is formedin Step 1 and a carbon-containing layer constituted by less than oneatomic layer is formed in Step 2, a part of the surface layer isnitrided in the same way. In this case, similarly, so as not to nitridethe entire second layer, nitriding is performed in a condition where thenitriding reaction of the second layer is not saturated.

Thereafter, the valve 243 d of the fourth gas supply pipe 232 d isclosed to interrupt the supply of NH₃ gas. At this time, in a statewhere the APC valve 244 of the exhaust pipe 231 is opened, the inside ofthe process chamber 201 is vacuum-evacuated by using the vacuum pump 246so that NH₃ gas remaining in the process chamber 201 withoutparticipating in a reaction or after participating in the nitridingreaction can be removed from the inside of the process chamber 201.Furthermore, at this time, in a state where the valve 243 h is opened,supply of N₂ gas to the inside of the process chamber 201 is continued.Owing to this, NH₃ gas remaining in the process chamber 201 withoutparticipating in a reaction or after participating in the nitridingreaction can be removed from the inside of the process chamber 201 moreeffectively.

As a nitrogen-containing gas, not only NH₃ gas but also another gas suchas N₂ gas, NF₃ gas, or N₃H₈ gas may be used.

By setting the above-described Step 1 to Step 3 to one cycle andrepeating this cycle at least once, a thin film includes silicon (firstelement), carbon (second element), and nitrogen (third element), thatis, a silicon carbonitride (SiCN) film can be formed on each of thewafers 200 to a predetermined thickness. Preferably, the cycle may berepeated a plurality of times.

In Step 2, the pressure of the inside of the process chamber 201, or thepressure of the inside of the process chamber 201 and the gas supplytime are controlled to be higher or longer than the pressure of theinside of the process chamber 201, or the pressure of the inside of theprocess chamber 201 and the gas supplying time in Step 2 when thesilicon carbonitride film having a stoichiometric composition is formed.By controlling the process conditions in this way, as compared with thecase where the silicon carbonitride film is formed to have thestoichiometric composition, carbon can be excessively supplied in Step 2(refer to section (B) in FIG. 10). Therefore, owing to the excessivesupply of carbon in Step 2, a region (silicon exposed region) of thesecond layer that can be nitrided in Step 3 is reduced. That is, ascompared with the case where the silicon carbonitride film is formed tohave the stoichiometric composition, an excessive number of carbon atomsare supplied in Step 2, and thus, in Step 3, the nitriding reaction ofthe second layer is restricted. In this way, the composition ratio ofthe silicon carbonitride (SiCN) film can be controlled in a manner suchthat carbon (C) is excessive as compare with nitrogen (N) in terms ofthe stoichiometric composition.

In the upper side of FIG. 10, schematic partial section views of a waferare shown to explain reaction states of steps during which a SiCN filmis formed to have a stoichiometric composition. In the lower side ofFIG. 10, schematic partial section views of a wafer are shown to explainreaction states of steps during which carbon (C) is excessively suppliedto form a SiCN film having excessive carbon (C) as compared withnitrogen (N) in terms of stoichiometric composition. Section (A) tosection (C) of FIG. 10 illustrate reaction states of Step 1 to Step 3,respectively.

Alternatively, in Step 3, the pressure of the inside of the processchamber 201, or the pressure of the inside of the process chamber 201and the gas supply time are controlled to be lower or shorter than thepressure of the inside of the process chamber 201, or the pressure ofthe inside of the process chamber 201 and the gas supplying time in Step3 when the silicon carbonitride film having the stoichiometriccomposition is formed. By controlling the process conditions in thisway, as compared with the case where the silicon carbonitride film isformed to have the stoichiometric composition, nitrogen can beinsufficiently supplied in Step 3 (refer to section (C) in FIG. 11).Therefore, owing to the insufficient supply of nitrogen in Step 3, thenitriding reaction of the second layer is restricted in Step 3. That is,as compared with the case where the silicon carbonitride film is formedto have the stoichiometric composition, an insufficient number ofnitrogen atoms are supplied in Step 3, and thus, in Step 3, thenitriding reaction of the second layer is restricted. In this way, thecomposition ratio of the silicon carbonitride (SiCN) film can becontrolled in a manner such that carbon (C) is excessive as compare withnitrogen (N) in terms of the stoichiometric composition.

In the upper side of FIG. 11, schematic partial section views of a waferare shown to explain reaction states of steps during which a SiCN filmis formed to have a stoichiometric composition. In the lower side ofFIG. 11, schematic partial section views of a wafer are shown to explainreaction states of steps during which nitrogen (N) is insufficientlysupplied to form a SiCN film having excessive carbon (C) as comparedwith nitrogen (N) in terms of stoichiometric composition. Section (A) tosection (C) of FIG. 11 illustrate reaction states of Step 1 to Step 3,respectively.

After a silicon carbonitride film having a predetermined composition andthickness is formed in the film-forming process, gas purge, replacementwith inert gas, return to atmospheric pressure, boat unloading, andwafer discharging are performed in the same way as in the firstsequence.

In the above-described example of the second sequence of the currentembodiment, a silicon-containing gas, a carbon-containing gas, and anitrogen-containing gas are respectively used as a firstelement-containing gas, a second element-containing gas, and a thirdelement-containing gas, so as to form a SiCN film; however, the presentinvention is not limited to the example but various changes andmodifications can be made within the scope and spirit of the presentinvention.

For example, a silicon-containing gas, a nitrogen-containing gas, and anoxygen-containing gas may be used as a first element-containing gas, asecond element-containing gas, and a third element-containing gas,respectively, so as to form a silicon oxynitride (SiON) film; or asilicon-containing gas, a boron-containing gas, and anitrogen-containing gas may be used as a first element-containing gas, asecond element-containing gas, and a third element-containing gas,respectively, so as to form a silicon boron nitride (SiBN) film. Inaddition, for example, a boron-containing gas, a carbon-containing gas,and a nitrogen-containing gas may be used as a first element-containinggas, a second element-containing gas, and a third element-containinggas, respectively, so as to form a boron carbonitride (BCN) film; analuminum-containing gas, a boron-containing gas, and anitrogen-containing gas may be used as a first element-containing gas, asecond element-containing gas, and a third element-containing gas,respectively, so as to form an aluminum boron nitride (AlBN) film; or asilicon-containing gas, a carbon-containing gas, and anoxygen-containing gas may be used as a first element-containing gas, asecond element-containing gas, and a third element-containing gas,respectively, so as to form a silicon oxycarbide (SiOC) film.Furthermore, a titanium-containing gas, an aluminum-containing gas, anda nitrogen-containing gas may be used as a first element-containing gas,a second element-containing gas, and a third element-containing gas,respectively, so as to form a titanium aluminum nitride (TiAlN) film; ora silicon-containing gas, an aluminum-containing gas, and anitrogen-containing gas may be used as a first element-containing gas, asecond element-containing gas, and a third element-containing gas,respectively, so as to form a silicon aluminum nitride (SiAlN) film. Inaddition, gases such as exemplified in the description of the firstsequence may also be used.

As explained above, according to the second sequence of the currentembodiment, a semiconductor element such as silicon (Si) or boron (B),or a metal element such as aluminum (Al) or titanium (Ti) may be used asa first element; an element such as nitrogen (N), carbon (C), or oxygen(O), or a metal such as aluminum (Al) may be used as a second element;and an element such as nitrogen (N) or oxygen (O) may be used as a thirdelement.

(Third Sequence) Next, a third sequence will now be described accordingto an embodiment. FIG. 5 is a view illustrating gas supply timing in thethird sequence according to an embodiment of the present invention; FIG.12 is a schematic view illustrating formation of a silicon boron carbonnitride film on a wafer in the third sequence according to theembodiment of the present invention; FIG. 13 is a schematic viewillustrating a case where carbon is excessively supplied in Step 2 ofthe third sequence according to the embodiment of the present invention;and FIG. 14 is a schematic view illustrating a case where nitrogen isinsufficiently supplied in Step 4 of the third sequence according to theembodiment of the present invention. The third sequence of the currentembodiment relates to a method of controlling a composition ratio offour elements.

The third sequence of the current embodiment includes a process offorming a first layer including a first element on a wafer 200 bysupplying a gas containing the first element (a first element-containinggas) to the inside of a process vessel in which the wafer 200 isaccommodated;

a process of forming a second layer including the first element and asecond element by supplying a gas containing the second element (secondelement-containing gas) to the inside of the process vessel, wherein thesecond layer is formed by forming a layer including the second elementon the first layer, or the second layer is formed by modifying the firstlayer;

a process of forming a third layer including the first element, thesecond element, and a third element by supplying a gas containing thethird element (the third element-containing gas) to the inside of theprocess vessel, wherein the third layer is formed by forming a layerincluding the third element on the second layer, or the third layer isformed by modifying the second layer; and

a process of forming a fourth layer including the first to thirdelements and a fourth element by supplying a gas containing the fourthelement (a fourth element-containing gas) to the inside of the processvessel to modify the third layer, wherein the process of forming thefirst layer, the process of forming the second layer, the process offorming the third layer, and the process of forming the fourth layer areset to one cycle, and the cycle is repeated at least once so as to forma thin film including the first to fourth elements and having apredetermined thickness.

In the third sequence, the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in one process of the process of forming of the firstlayer, the process of forming of the second layer, the process offorming of the third layer, and the process of forming of the fourthlayer are controlled to be higher or longer than the pressure of theinside of the process vessel, or the pressure of the inside of theprocess vessel and the time of supplying the gas in the one process whenthe thin film having a stoichiometric composition is formed.

Alternatively, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the other process of the process of forming of the firstlayer, the process of forming of the second layer, the process offorming of the third layer, and the process of forming of the fourthlayer are controlled to be lower or shorter than the pressure of theinside of the process vessel, or the pressure of the inside of theprocess vessel and the time of supplying the gas in the other processwhen the thin film having the stoichiometric composition is formed.

In this way, one of the elements of the thin film can be excessive ascompared with the others in terms of the stoichiometric composition.

In the case of a thin film made of a four-element thin film, thestoichiometric composition is not unique unlike the case of atwo-element thin film but is two or more like the case of athree-element thin film. In the third sequence of the currentembodiment, a thin film is formed in a manner such that the thin filmhas a composition ratio different from any of the stoichiometriccompositions.

The process of forming the first layer is the same as the process offorming the first layer in the second sequence. That is, thingsregarding the process of forming the first layer, such as processconditions, motivated reaction, layers, layer thickness, examples of thefirst element, examples of the first element-containing gas, andexamples of the first layer, are the same as those regarding the processof forming the first layer in the second sequence.

The process of forming the second layer is the same as the process offorming the second layer in the second sequence. That is, thingsregarding the process of forming the second layer, such as processconditions, a gas activating method, motivated reaction, layers,examples of the second element, examples of the secondelement-containing gas, and examples of the second layer, are the sameas those regarding the process of forming the second layer in the secondsequence.

In the process of forming the third layer, the third element-containinggas is activated by plasma or heat and is then supplied, so that a layerincluding the third element and constituted by less than one to severalatomic layers can be formed on the second layer or the second layer canbe modified by reaction between a part of the second layer and the thirdelement-containing gas. In this way, the third layer including the firstto third elements is formed.

In the case where the third layer is formed by forming a layer includingthe third element on the second layer, the layer including the thirdelement may be a third element layer or a third element-containing gasadsorption layer. The third element-containing gas adsorption layerincludes an adsorption layer formed of a material decomposed from thethird element-containing gas. The third element layer is a general termfor a layer made of the third element, such as a continuous layer, adiscontinuous layer, and a thin film in which such layers areoverlapped. In addition, a continuous layer formed of the third elementmay also be called “a thin film.” In addition, the thirdelement-containing gas adsorption layer is a term including a continuouschemical adsorption layer and a discontinuous chemical adsorption layerthat are formed of molecules of the third element-containing gas ormolecules of a material decomposed from the third element-containinggas. Preferably, the layer including the third element may be adiscontinuous chemical adsorption layer formed of molecules of the thirdelement-containing gas or molecules of a material decomposed from thethird element-containing gas, that is, the layer including the thirdelement may be a chemical adsorption layer constituted by less than oneatomic layer, so as to improve the controllability of the compositionratio of the thin film.

In the case where the third layer is formed by modifying the secondlayer, the second layer is modified by the same method as the methodused for modifying the second layer in the process of forming the thirdlayer in the second sequence.

The third element-containing gas may be supplied after being activatedby plasma or heat. FIG. 5 illustrates an example where the thirdelement-containing gas is supplied after being activated by heat, thatis, an example for causing a soft reaction.

In the process of forming the fourth layer, the fourthelement-containing gas is activated by plasma or heat and is thensupplied to the third layer, so as to modify the third layer for formingthe fourth layer including the first to fourth elements. For example, ifthe third layer is formed to have the first to third elements and beconstituted by several atomic layers in the process of forming the thirdlayer, the surface atomic layer of the several atomic layers maypartially or entirely be allowed to react with the fourthelement-containing gas. Alternatively, the surface atomic layer and thenext lower atomic layers among the several atomic layers of the thirdlayer formed of the first to third elements may be allowed to react withthe fourth element-containing gas. However, in the case where the thirdlayer is constituted by the several atomic layers including the first tothird elements, it may be preferable that only the surface atomic layerof the third layer be modified because the composition ratio of the thinfilm can be controlled more easily. Preferably, the fourth element maybe an element that cannot turn into solid by itself. The fourthelement-containing gas may be supplied after being activated by plasmaor heat. FIG. 5 illustrates an example where the fourthelement-containing gas is supplied after being activated by heat, thatis, an example of causing a soft reaction for performing a softmodification.

A method, such as a method of controlling the composition ratio of thethin film in a manner such that the first element is excessive ascompared with the second element in terms of the stoichiometriccomposition, is the same as that used in the first sequence or thesecond sequence.

A method, such as a method of controlling the composition ratio of thethin film in a manner such that the second element is excessive ascompared with the third element in terms of the stoichiometriccomposition or the third element is excessive as compared with thesecond element in terms of the stoichiometric composition, is the sameas that used in the second sequence.

In the case where the composition ratio of the thin film is controlledin a manner such that the second or third element is excessive ascompared with the fourth element in terms of the stoichiometriccomposition or the fourth element is excessive as compared with thesecond or third element in terms of the stoichiometric composition, thecomposition ratio is controlled based on one of the elements.

For example, in the case where the composition ratio of the thin film iscontrolled in a manner such that the second element is excessive ascompared with the fourth element in terms of the stoichiometriccomposition, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming the second layer are controlled to behigher or longer than the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in the process of forming the second layer when thethin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the second element can be excessively supplied in theprocess of forming the second layer. Therefore, owing to the excessivesupply of the second element in the process of forming the second layer,a region of the third layer that can be modified in the process offorming the fourth layer is reduced. That is, as compared with the casewhere the thin film is formed to have the stoichiometric composition, anexcessive number of atoms of the second element are supplied in theprocess of forming the second layer, and thus, in the process of formingthe fourth layer, the modification reaction of the third layer can berestricted.

Alternatively, the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming the fourth layer are controlled to belower or shorter than the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in the process of forming the fourth layer when thethin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the fourth element can be insufficiently supplied in theprocess of forming the fourth layer. Therefore, owing to theinsufficient supply of the fourth element in the process of forming thefourth layer, the modification reaction of the third layer can berestricted in the process of forming the fourth layer. That is, ascompared with the case where the thin film is formed to have thestoichiometric composition, an insufficient number of atoms of thefourth element are supplied in the process of forming the fourth layer,and thus, in the process of forming the fourth layer, the modificationreaction of the third layer can be restricted.

In addition, for example, in the case where the composition ratio of thethin film is controlled in a manner such that the fourth element isexcessive as compared with the second element in terms of thestoichiometric composition, the pressure of the inside of the processvessel, or the pressure of the inside of the process vessel and the timeof supplying the gas in the process of forming of the second layer arecontrolled to be lower or shorter than the pressure of the inside of theprocess vessel, or the pressure of the inside of the process vessel andthe time of supplying the gas in the process of the second layer whenthe thin film having the stoichiometric composition is formed. Bycontrolling the process conditions in this way, as compared with thecase where the thin film is formed to have the stoichiometriccomposition, the second element can be insufficiently supplied in theprocess of forming the second layer. Therefore, owing to theinsufficient supply of the second element in the process of forming thesecond layer, a layer including the second element is formed in asmaller region or modification reaction of the first layer isrestricted. As a result, the fourth element becomes excessive ascompared with the second element in terms of the stoichiometriccomposition.

If the second element is insufficiently supplied in the process offorming the second layer, a region of the third layer that can bemodified in the process of forming the fourth layer is increased. Inthis case, if the pressure of the inside of the process vessel, or thepressure of the inside of the process vessel and the time of supplyingthe gas in the process of forming the fourth layer are controlled to behigher or longer than the pressure of the inside of the process vessel,or the pressure of the inside of the process vessel and the time ofsupplying the gas in the process of forming the fourth layer when thethin film having the stoichiometric composition is formed, the fourthelement can be excessively supplied in the process of forming the fourthlayer, and thus the fourth element can be controlled to be muchexcessive as compared with the second element in terms of thestoichiometric composition. That is, by a combination of insufficientsupply of the second element in the process of forming the second layerand excessive supply of the fourth element in the process of forming thefourth layer, the modification reaction of the third layer can befacilitated in the process of forming the fourth layer, and thus thecomposition ratio of the thin film can be controlled in a manner suchthat the fourth element is much excessive as compared with the secondelement in terms of the stoichiometric composition.

Hereinafter, the third sequence of the current embodiment will bedescribed more specifically. In the following description, anexplanation will be given on an example where a silicon boron carbonnitride (SiBCN) film is formed on a substrate as an insulating filmaccording to the sequence shown in FIG. 5 under the conditions wheresilicon (Si) is a first element, carbon (C) is a second element, boron(B) is a third element, nitrogen (N) is a fourth element, DCS gas whichis a silicon-containing gas is used as a first element-containing gas,C₃H₆ gas which is a carbon-containing gas is used as a secondelement-containing gas, BCl₃ gas which is a boron-containing gas is usedas a third element-containing gas, and NH₃ gas which is anitrogen-containing gas is used as a fourth element-containing gas.Furthermore, in the following description of the example, thecomposition ratio of the silicon boron carbon nitride film is controlledsuch that carbon (C) is excessive as compared with nitrogen (N) in termsof the stoichiometric composition. In addition, in the example, thefirst gas supply system constitutes a silicon-containing gas supplysystem (first element-containing gas supply system), the second gassupply system constitutes a carbon-containing gas supply system (secondelement-containing gas supply system), the third gas supply systemconstitutes a boron-containing gas supply system (thirdelement-containing gas supply system), and the fourth gas supply systemconstitutes a nitrogen-containing gas supply system (fourthelement-containing gas supply system).

Wafer charging, boat loading, pressure adjustment, temperatureadjustment, and wafer rotation are performed in the same way as in thesecond sequence, and then, the following four steps are sequentiallyperformed.

[Step 1]

Step 1 is performed in the same way as Step 1 of the second sequence.That is, things regarding Step 1, such as process conditions, motivatedreaction, layers, layer thickness, examples of the first element,examples of the first element-containing gas, and examples of the firstlayer, are the same as those regarding Step 1 of the second sequence(refer to section (A) of FIG. 12).

[Step 2]

Step 2 is performed in the same way as Step 2 of the second sequence.That is, things regarding Step 2, such as process conditions, a gasactivating method, motivated reaction, layers, examples of the secondelement, examples of the second element-containing gas, and examples ofthe second layer, are the same as those regarding Step 2 of the secondsequence (refer to section (B) of FIG. 12).

[Step 3]

After completing Step 2 and removing gas remaining in the processchamber 201, the valve 243 c of the third gas supply pipe 232 c isopened to allow a flow of BCl₃ gas through the third gas supply pipe 232c. The flowrate of the BCl₃ gas flowing through the third gas supplypipe 232 c is controlled by the MFC 241 c. Then, the BCl₃ gas issupplied to the inside of the process chamber 201 through the gas supplyholes 250 c of the third nozzle 249 c and is exhausted through theexhaust pipe 231. At this time, the valve 243 g is also opened to allowa flow of N₂ gas through the inert gas supply pipe 232 g. The N₂ gas issupplied to the inside of the process chamber 201 together with the BCl₃gas and is exhausted through the exhaust pipe 231.

At this time, the APC valve 244 is properly controlled so as to adjustthe inside pressure of the process chamber 201, for example, in therange of 50 Pa to 3000 Pa. The flowrate of the BCl₃ gas controlled bythe MFC 241 c is, for example, in the range of 100 sccm to 10000 sccm.The time during which wafers 200 are exposed to the BCl₃ gas, that is,gas supply time (exposing time) is in the range of, for example, 2seconds to 120 seconds. At this time, like in Step 1, the temperature ofthe heater 207 is set to a predetermined temperature so that thetemperature of the wafers 200 can be in the range of, for example, 300°C. to 650° C. In the case where the BCl₃ gas is activated by heat and issupplied, soft reaction can be caused, and thus a boron-containing layercan be easily formed (described later).

At this time, gas flowing in the process chamber 201 is BCl₃ gasactivated by heat and neither DCS gas nor C₃H₆ gas flows in the processchamber 201. Therefore, without causing a vapor-phase reaction, the BCl₃gas which is in an activated state is supplied to the wafers 200, and atthis time, as shown in section (C) of FIG. 12, a boron-containing layerconstituted by less than one atomic layer, that is, a discontinuousboron-containing layer, is formed on a layer which includes silicon andcarbon and is formed on each of the wafer 200 as a second layer in Step2. In this way, a third layer including silicon (first element), carbon(second element), and boron (third element) is formed. In some cases,according to conditions, a part of the second layer reacts with the BCl₃gas, and as a result, the second layer is modified (boronized) to form athird layer including silicon, nitrogen, and boron.

The boron-containing layer formed on the second layer may be a boronlayer (B-layer), a chemical adsorption layer of BCl₃, or a chemicaladsorption layer of B_(x)Cl_(y) (a material decomposed from BCl₃). Sinceboron does not couple with carbon although it couples with silicon, theboron layer is a discontinuous layer of boron, and the chemicaladsorption layer of BCl₃ or B_(x)Cl_(y) is a discontinuous chemicaladsorption layer formed of BCl₃ molecules or B_(x)Cl_(y) molecules.

Thereafter, the valve 243 c of the third gas supply pipe 232 c is closedto interrupt supply of BCl₃ gas. At this time, in a state where the APCvalve 244 of the exhaust pipe 231 is opened, the inside of the processchamber 201 is vacuum-evacuated by using the vacuum pump 246 so thatBCl₃ gas remaining in the process chamber 201 without participating in areaction or after participating in the formation of the boron-containinglayer can be removed from the inside of the process chamber 201.Furthermore, at this time, in a state where the valve 243 g is opened,supply of N₂ gas to the inside of the process chamber 201 is continued.Owing to this, BCl₃ gas remaining in the process chamber 201 withoutparticipating in a reaction or after participating in the formation ofthe boron-containing layer can be removed from the inside of the processchamber 201 more effectively.

As a boron-containing gas, not only BCl₃ gas, but also another gas suchas B₂H₆ gas may be used.

[Step 4]

After removing gas remaining in the process chamber 201, the valve 243 dof the fourth gas supply pipe 232 d is opened to allow a flow of NH₃ gasthrough the fourth gas supply pipe 232 d. The flowrate of the NH₃ gasflowing through the fourth gas supply pipe 232 d is controlled by theMFC 241 d. Then, the NH₃ gas is supplied to the inside of the bufferchamber 237 through the gas supply holes 250 d of the fourth nozzle 249d. At this time, high-frequency power is not applied across the firstrod-shaped electrode 269 and the second rod-shaped electrode 270. As aresult, the NH₃ gas supplied to the inside of the buffer chamber 237 isactivated by heat and is then supplied to the inside of the processchamber 201 through the gas supply holes 250 e while being exhaustedthrough the exhaust pipe 231. At this time, the valve 243 h is alsoopened to allow a flow of N₂ gas through the inert gas supply pipe 232h. Then, together with the NH₃ gas, the N₂ gas is supplied to the insideof the process chamber 201 and is exhausted through the exhaust pipe231.

When the NH₃ gas is activated by heat and is allowed to flow, the APCvalve 244 is properly controlled so as to adjust the inside pressure ofthe process chamber 201, for example, in the range of 50 Pa to 3000 Pa.The flowrate of the NH₃ gas controlled by the MFC 241 d is, for example,in the range of 100 sccm to 10000 sccm. The time during which the wafers200 are exposed to the NH₃ gas, that is, gas supply time (exposing time)is in the range of, for example, 2 seconds to 120 seconds. At this time,like in Step 1, the temperature of the heater 207 is set to apredetermined temperature so that the temperature of the wafers 200 canbe in the range of, for example, 300° C. to 650° C. Since it isdifficult to make the NH₃ gas reactive at the above-mentionedtemperature range of the wafers 200 due to a high reaction temperatureof the NH₃ gas, the process chamber 201 is kept at a relatively highpressure as mentioned above so as to activate the NH₃ gas by heat. Inthe case where the NH₃ gas is activated by heat and is supplied, softreaction can be caused for soft nitriding (described later).

At this time, gas flowing in the process chamber 201 isthermally-activated NH₃ gas, and neither DCS gas nor C₃H₆ gas flows inthe process chamber 201. Therefore, without causing a vapor-phasereaction, the activated NH₃ gas reacts with a part of the layerincluding silicon, carbon, and boron, that is, a part of the third layerformed on each of the wafers 200 in Step 3. As a result, the third layeris nitrided and modified into a fourth layer including silicon (firstelement), carbon (second element), boron (third element), and nitrogen(fourth element), that is, into a silicon boron carbon nitride (SiBCN)layer.

At this time, as shown in section (D) of FIG. 12, the nitriding reactionof the third layer is not saturated. For example, in the case where asilicon layer constituted by several atomic layers is formed in Step 1,a carbon-containing layer constituted by less than one atomic layer isformed in Step 2, and a boron-containing layer constituted by less thanone atomic layer is formed in Step 3, a part of the surface layer (thesurface atomic layer of the atomic layers) is nitrided. That is, aregion (silicon exposed region) of the surface layer that can benitrided is partially or entirely nitrided. In this case, so as not toentirely nitride the third layer, the nitriding of the third layer isperformed under a non-saturated condition. Alternatively, according toconditions, the surface atomic layer and the next lower atomic layersamong the atomic layers of the third layer can be nitrided; however, thecase where only the surface atomic layer is nitrided is preferablebecause the composition ratio of the silicon boron carbon nitride filmcan be controlled more easily. In addition, for example, in the casewhere a silicon layer constituted by one atomic layer or less than oneatomic layer is formed in Step 1, a carbon-containing layer constitutedby less than one atomic layer is formed in Step 2, and aboron-containing layer constituted by less than one atomic layer isformed in Step 3, a part of the surface layer is nitrided in the sameway. In this case, similarly, so as not to nitride the entire thirdlayer, nitriding is performed in a condition where the nitridingreaction of the third layer is not saturated.

Thereafter, the valve 243 d of the fourth gas supply pipe 232 d isclosed to interrupt the supply of NH₃ gas. At this time, in a statewhere the APC valve 244 of the exhaust pipe 231 is opened, the inside ofthe process chamber 201 is vacuum-evacuated by using the vacuum pump 246so that NH₃ gas remaining in the process chamber 201 withoutparticipating in a reaction or after participating in the nitridingreaction can be removed from the inside of the process chamber 201.Furthermore, at this time, in a state where the valve 243 h is opened,supply of N₂ gas to the inside of the process chamber 201 is continued.Owing to this, NH₃ gas remaining in the process chamber 201 withoutparticipating in a reaction or after participating in the nitridingreaction can be removed from the inside of the process chamber 201 moreeffectively.

As a nitrogen-containing gas, not only NH₃ gas but also another gas suchas N₂ gas, NF₃ gas, or N₃H₈ gas may be used.

By setting the above-described Step 1 to Step 4 to one cycle andrepeating this cycle at least once, a thin film includes silicon (firstelement), carbon (second element), boron (third element), and nitrogen(fourth element), that is, a silicon boron carbon nitride (SiBCN) filmcan be formed on each of the wafers 200 to a predetermined thickness.Preferably, the cycle may be repeated a plurality of times.

In Step 2, the pressure of the inside of the process chamber 201, or thepressure of the inside of the process chamber 201 and the gas supplytime are controlled to be higher or longer than the pressure of theinside of the process chamber 201, or the pressure of the inside of theprocess chamber 201 and the gas supplying time in Step 2 when thesilicon boron carbon nitride film having a stoichiometric composition isformed. By controlling the process conditions in this way, as comparedwith the case where the silicon boron carbon nitride film is formed tohave the stoichiometric composition, carbon can be excessively suppliedin Step 2 (refer to section (B) in FIG. 13). Therefore, owing to theexcessive supply of carbon in Step 2, a region (silicon exposed region)of the third layer that can be nitrided in Step 4 is reduced. That is,as compared with the case where the silicon boron carbon nitride film isformed to have the stoichiometric composition, an excessive number ofcarbon atoms are supplied in Step 2, and thus, in Step 4, the nitridingreaction of the third layer is restricted. In this way, the compositionratio of the silicon boron carbon nitride (SiBCN) film can be controlledin a manner such that carbon (C) is excessive as compare with nitrogen(N) in terms of the stoichiometric composition.

In the upper side of FIG. 13, schematic partial section views of a waferare shown to explain reaction states of steps during which a SiBCN filmis formed to have a stoichiometric composition. In the lower side ofFIG. 13, schematic partial section views of a wafer are shown to explainreaction states of steps during which carbon (C) is excessively suppliedto form a SiBCN film having excessive carbon (C) as compared withnitrogen (N) in terms of stoichiometric composition. Section (A) tosection (D) of FIG. 13 illustrate reaction states of Step 1 to Step 4,respectively.

Alternatively, in Step 4, the pressure of the inside of the processchamber 201, or the pressure of the inside of the process chamber 201and the gas supply time are controlled to be lower or shorter than thepressure of the inside of the process chamber 201, or the pressure ofthe inside of the process chamber 201 and the gas supplying time in Step4 when the silicon boron carbon nitride film having a stoichiometriccomposition is formed. By controlling the process conditions in thisway, as compared with the case where the silicon boron carbon nitridefilm is formed to have the stoichiometric composition, nitrogen can beinsufficiently supplied in Step 4. Therefore, owing to the insufficientsupply of nitrogen in Step 4, the nitriding reaction of the third layeris restricted in Step 4. That is, as compared with the case where thesilicon boron carbon nitride film is formed to have the stoichiometriccomposition, an insufficient number of nitrogen atoms are supplied inStep 4, and thus, in Step 4, the nitriding reaction of the third layeris restricted. In this way, the composition ratio of the silicon boroncarbon nitride (SiBCN) film can be controlled in a manner such thatcarbon (C) is excessive as compare with nitrogen (N) in terms of thestoichiometric composition.

In the upper side of FIG. 14, schematic partial section views of a waferare shown to explain reaction states of steps during which a SiBCN filmis formed to have a stoichiometric composition. In the lower side ofFIG. 14, schematic partial section views of a wafer are shown to explainreaction states of steps during which nitrogen (N) is insufficientlysupplied to form a SiBCN film having excessive carbon (C) as comparedwith nitrogen (N) in terms of stoichiometric composition. Section (A) tosection (D) of FIG. 14 illustrate reaction states of Step 1 to Step 4,respectively.

After a silicon boron carbon nitride film having a predeterminedcomposition and thickness is formed in the film-forming process, gaspurge, replacement with inert gas, return to atmospheric pressure, boatunloading, and wafer discharging are performed in the same way as in thesecond sequence.

In the above-described example of the third sequence of the currentembodiment, a silicon-containing gas, a carbon-containing gas, aboron-containing gas, and a nitrogen-containing gas are respectivelyused as a first element-containing gas, a second element-containing gas,a third element-containing gas, and a fourth element-containing gas, soas to form a SiBCN film; however, the present invention is not limitedto the example but various changes and modifications can be made withinthe scope and spirit of the present invention.

For example, a silicon-containing gas, a carbon-containing gas, anoxygen-containing gas, and a nitrogen-containing gas may be used as afirst element-containing gas, a second element-containing gas, a thirdelement-containing gas, and a fourth element-containing gas,respectively, so as to form a silicon oxygen carbon nitride (SiOCN)film. In this case, alternatively, a nitrogen-containing gas and anoxygen-containing gas may be used as a third element-containing gas anda fourth element-containing gas, respectively. In addition, for example,a silicon-containing gas, an aluminum-containing gas, atitanium-containing gas, and a nitrogen-containing gas may be used as afirst element-containing gas, a second element-containing gas, a thirdelement-containing gas, and a fourth element-containing gas,respectively, so as to form a silicon aluminum titanium nitride(SiAITiN) film. Furthermore, for example, a silicon-containing gas, acarbon-containing gas, a silicon-containing gas, and anitrogen-containing gas may be used as a first element-containing gas, asecond element-containing gas, a third element-containing gas, and afourth element-containing gas, respectively, so as to form a siliconcarbonitride (SiCN). In this way, a three-element thin film can beformed. That is, for example, by using the same gas as the firstelement-containing gas and the third element-containing gas, the thirdsequence can be used for forming a three-element thin film. In addition,gases such as exemplified in the description of the first sequence mayalso be used.

In the third sequence of the current embodiment, a semiconductor elementsuch as silicon (Si) or boron (B), or a metal element such as aluminum(Al) or titanium (Ti) may be used as a first element; an element such asnitrogen (N), boron (B), carbon (C), or oxygen (O), or a metal elementsuch as aluminum (Al) or titanium (Ti) may be used as a second elementor a third element; and an element such as nitrogen (N) or oxygen (O)may be used as a fourth element.

In a conventional CVD method, a plurality of kinds of gases including aplurality of elements constituting a thin film to be formed aresimultaneously supplied. In this case, so as to control the compositionratio of a thin film to be formed, for example, the ratio of gas supplyflowrates may be controlled when gases are supplied. In this case,although supply conditions such as the temperature of a substrate, thepressure of the inside of a process chamber, and gas supply time areadjusted when gases are supplied, the composition ratio of the thin filmis not controlled.

Furthermore, in the case of an ALD method, a plurality of kinds of gasesincluding a plurality of elements constituting a thin film to be formedare supplied in turns. In this case, so as to control the compositionratio of a thin film to be formed, for example, gas supply flowrate andgas supply time may be controlled when each gas is supplied. In the ALDmethod, a source gas is supplied to a substrate for the purpose ofsaturating adsorption of the source gas on the substrate, and thus,pressure control is unnecessary for the inside of a process chamber.That is, since saturation of source gas adsorption occurs at a pressureequal to or lower than a predetermined pressure at which the source gasis adsorbed for a given reaction temperature, only if the pressure ofthe inside of the process chamber is kept equal to or lower than thepredetermined pressure, adsorption of the source gas can be saturated atany pressures in the range. Therefore, generally, in a film-formingprocess performed by an ALD method, the inside pressure of a processchamber is allowed to be determined according to the exhausting abilityof a substrate processing apparatus in relation with the amount ofsupplied gas. However, if it is configured to vary the inside pressureof a process chamber, chemical adsorption of a source gas on the surfaceof a substrate may be hindered, or reaction may become similar to CVDreaction, thereby making it difficult to perform a film-forming processby an ALD method. In addition, since an ALD reaction (adsorptionsaturation, surface reaction) is repeatedly performed so as to form athin film to a predetermined thickness by an ALD method, if the ALDreaction is not sufficiently performed to a saturation level in eachiteration, deposition may also be insufficient, and a sufficientdeposition rate cannot be obtained. Therefore, in the case of an ALDmethod, it is difficult to control the composition ratio of a thin filmby controlling the inside pressure of a process chamber.

However, according to the embodiments of the present invention, in anyone of the first sequence, the second sequence, and the third sequence,a plurality of kinds of gases including a plurality of elementsconstituting a thin film to be formed are alternately supplied underconditions where CVD reaction is caused; and the pressure of the insideof the process chamber, or the pressure of the inside of the processchamber and the gas supply time are controlled in each step, so as tocontrol the composition ratio of the thin film.

In the case where the composition ratio of a thin film is controlled bycontrolling the pressure of the inside of the process chamber in eachstep, influence of mechanical deviation between different substrateprocessing apparatuses can be reduced. That is, by using the samecontrol method among different substrate processing apparatuses, thecomposition ratio of thin films can be equally controlled. In this case,if gas supply time is also controlled in each step, the compositionratio of a thin film can be finely controlled, and thus thecontrollability of the composition ratio of a thin film can be improved.Furthermore, by controlling the pressure of the inside of the processchamber in each step, the composition ratio of a thin film can becontrolled while increasing the film-forming rate. That is, bycontrolling the pressure of the inside of the process chamber, thecomposition ratio of a thin film can be controlled, for example, whileincreasing the growth rate of a silicon-containing layer in Step 1 ofeach sequence. As explained above, according to the embodiments of thepresent invention, although a different substrate processing apparatusis used, the composition ratio of a thin film can be equally controlledby using the same control method, and thus the controllability of thecomposition ratio of a thin film can be improved, and furthermore, thefilm-forming rate, that is, productivity can be improved.

In a film-forming process by an ALD method, if the composition ratio ofa thin film is controlled by adjusting the supply flowrate or supplytime of gas in each step, the influence of mechanical deviation amongdifferent substrate processing apparatuses is increased. That is,although the same control is performed among different substrateprocessing apparatuses, the composition ratio of a thin film is notequally controlled. For example, although the supply flowrate and timeof gas are set to the same values for different substrate processingapparatuses, the inside pressures of process chambers are not equal dueto mechanical deviation. Therefore, since the inside pressures of theprocess chambers are different from one substrate processing apparatusto another, control for a desired composition ratio cannot be performedin the same manner among different substrate processing apparatuses. Inaddition, if the inside pressure of the process chamber is varied fromone substrate processing apparatus to another, chemical adsorption of asource gas on the surface of a substrate may be hindered, or reactionmay become similar to CVD reaction, thereby making it difficult toperform a film-forming process properly according to an ALD method.

First Example

Next, a first example will be described.

By using silicon (Si) as a first element and nitrogen (N) as a secondelement, a silicon nitride (SiN) film was formed while controlling thecomposition ratio of the silicon nitride film according to the firstsequence of the embodiment, and then, the composition ratio wasmeasured. DCS gas was used as a first element-containing gas, and NH₃gas was used as a second element-containing gas. The composition ratiocontrol was performed by adjusting pressure or gas supply time (exposingtime) which is a composition ratio control factor. As pressure or gassupply time was increased, reaction was increased, and thus thethickness of a layer was increased in a corresponding process. That is,a more amount of a substance (more atoms) was supplied in the process.However, if a reactive species of which the adsorption or reaction couldbe saturated was used, in some cases, the thickness of the layer mightnot be increased equal to or greater than, for example, that of oneatomic layer.

First, a silicon nitride (Si₃N₄) film having standard stoichiometriccomposition (N/Si÷1.33) was formed on a wafer. At that time, processconditions were set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 532 Pa (4 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 24 seconds

By adjusting process conditions based on the above-listed standardprocess conditions, it was tried to form a silicon nitride (Si₄N₄) filmhaving a composition ratio of N/Si÷1.

By changing the exposing time to DCS gas from 12 seconds to 48 secondsin the first step, a Si₄N₄ film having a high silicon content could beformed. That is, by increasing the exposing time to DCS gas longer thanthat of the standard process conditions in the first step, a Si₄N₄ filmhaving a high silicon content could be formed. Except for the exposingtime to DCS gas in the first step, other process conditions were setequal to the standard process conditions. That is, the processconditions were set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 48 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 532 Pa (4 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 24 seconds

Alternatively, by changing the pressure inside the process chamber from133 Pa (1 Torr) to 266 Pa (2 Torr) in the first step, a Si₄N₄ filmhaving a high silicon content could be formed. That is, by increasingthe pressure inside the process chamber higher than that of the standardprocess conditions in the first step, a Si₄N₄ film having a high siliconcontent could be formed. Except for the pressure inside the processchamber in the first step, other process conditions were set equal tothe standard process conditions. That is, the process conditions wereset as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 266 Pa (2 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 532 Pa (4 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 24 seconds

Alternatively, by changing the exposing time to NH₃ gas from 24 secondsto 6 seconds in the second step, a Si₄N₄ film having a relatively highsilicon content could be formed because the nitrogen content wasreduced. That is, by decreasing the exposing time to NH₃ gas shorterthan that of the standard process conditions in the second step, a Si₄N₄film having a high silicon content could be formed. Except for theexposing time to NH₃ in the second step, other process conditions wereset equal to the standard process conditions. That is, the processconditions were set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 532 Pa (4 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 6 seconds

Alternatively, by changing the pressure inside the process chamber from532 Pa (4 Torr) to 133 Pa (1 Torr) in the second step, similarly, aSi₄N₄ film having a high silicon content could be formed. That is, bydecreasing the pressure inside the process chamber lower than that ofthe standard process conditions in the second step, a Si₄N₄ film havinga high silicon content could be formed. That is, the process conditionswere set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 24 seconds

By changing the Si/N composition ratio of a silicon nitride film asdescribed in the example, the charge density (film property) of thesilicon nitride film can be controlled, and thus the silicon nitridefilm can be used as a charge trapping film of a flash memory. Inaddition, by changing the Si/N composition ratio of a silicon nitridefilm as described in the example, the optical refractive index orabsorption coefficient of the silicon nitride film can be controlled,and thus the silicon nitride film can be used as an antireflection filmin a lithograph process.

Second Example

Next, a second example will be described.

By using silicon (Si) as a first element, carbon (C) as a secondelement, and nitrogen (N) as a third element, a silicon carbonitride(SiCN) film was formed while controlling the composition ratio of thesilicon carbonitride film according to the second sequence of theembodiment, and then, the composition ratio was measured. DCS gas wasused as a first element-containing gas, C₃H₆ gas was used as a secondelement-containing gas, and NH₃ gas was used as a thirdelement-containing gas. The composition ratio control was performed byadjusting pressure or gas supply time (exposing time) which is acomposition ratio control factor. Like in the case of controlling thecomposition ratio of a two-element film, when the composition ratio of athree-element film was controlled, as pressure or gas supply time wasincreased, reaction was increased, and thus the thickness of a layer wasincreased in a corresponding process. That is, more atoms were suppliedin the process. However, if a reactive species of which the adsorptionor reaction could be saturated was used, in some cases, the thickness ofthe layer might not be increased equal to or greater than, for example,that of one atomic layer.

First, a silicon carbonitride film having a standard composition (8 atom% of carbon) was formed on a wafer. At that time, process conditionswere set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of C₃H₆ gas: 1 slm

Exposing time to C₃H₆ gas: 8 seconds

(Third Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 931 Pa (7 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 18 seconds

By adjusting process conditions based on the above-listed standardprocess conditions, it was tried to form a silicon carbonitride (SiCN)film having 16 atom % of carbon.

By changing the exposing time to C₃H₆ gas from 8 seconds to 16 secondsin the second step, a SiCN film having a high carbon content could beformed. That is, by increasing the exposing time to C₃H₆ gas longer thanthat of the standard process conditions in the second step, a SiCN filmhaving a high carbon content could be formed. As the content of carbonwas increased, the content of nitrogen was decreased. Except for theexposing time to C₃H₆ gas in the second step, other process conditionswere set equal to the standard process conditions. That is, the processconditions were set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of C₃H₆ gas: 1 slm

Exposing time to C₃H₆ gas: 16 seconds

(Third Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 931 Pa (7 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 18 seconds

Alternatively, by changing the pressure inside the process chamber from133 Pa (1 Torr) to 266 Pa (2 Torr) in the second step, a SiCN filmhaving a high carbon content could be formed. That is, by increasing thepressure inside the process chamber higher than that of the standardprocess conditions in the second step, a SiCN film having a high carboncontent could be formed. As the content of carbon was increased, thecontent of nitrogen was decreased. Except for the pressure inside theprocess chamber in the second step, other process conditions were setequal to the standard process conditions. That is, the processconditions were set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 266 Pa (2 Torr)

Flowrate of C₃H₆ gas: 1 slm

Exposing time to C₃H₆ gas: 8 seconds

(Third Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 931 Pa (7 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 18 seconds

Alternatively, by changing the exposing time to NH₃ gas from 18 secondsto 6 seconds in the third step, a SiCN film having a relatively highcarbon content could be formed because the content of nitrogen wasreduced. That is, by decreasing the exposing time to NH₃ gas shorterthan that of the standard process conditions in the third step, a SiCNfilm having a high carbon content could be formed. Except for theexposing time to NH₃, other process conditions were set equal to thestandard process conditions. That is, the process conditions were set asfollows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of C₃H₆ gas: 1 slm

Exposing time to C₃H₆ gas: 8 seconds

(Third Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 931 Pa (7 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 6 seconds

Alternatively, by changing the pressure inside the process chamber from931 Pa (7 Torr) to 266 Pa (2 Torr) in the third step, similarly, a SiCNfilm having a high carbon content could be formed. That is, bydecreasing the pressure inside the process chamber lower than that ofthe standard process conditions in the third step, a SiCN film having ahigh silicon content could be formed. Except for the pressure inside theprocess chamber, other process conditions were set equal to the standardprocess conditions. That is, the process conditions were set as follows.

(First Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of DCS gas: 1 slm

Exposing time to DCS gas: 12 seconds

(Second Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 133 Pa (1 Torr)

Flowrate of C₃H₆ Gas: 1 Slm

Exposing Time to C₃H₆ Gas: 8 Seconds

(Third Step)

Temperature in process chamber: 630° C.

Pressure in process chamber: 266 Pa (2 Torr)

Flowrate of NH₃ gas: 9 slm

Exposing time to NH₃ gas: 18 seconds

By changing the C/N composition ratio of a silicon carbonitride film asdescribed in the example, the etch resistance (film property) of thesilicon carbonitride film can be improved, and thus the siliconcarbonitride film can be used as an etch stopper film.

In the case of forming silicon oxynitride (SiON) film while controllingthe composition ratio of the silicon oxynitride film according to thesecond sequence of the embodiment by using silicon (Si) as a firstelement, oxygen (O) as a second element, and nitrogen (N) as a thirdelement, the O/N composition ratio of the silicon oxynitride film can bevaried so as to reduce the dielectric constant of the silicon oxynitridefilm lower than that of a Si₃N₄ film and improve the etch resistance ofthe silicon oxynitride film superior that of a SiO₂ film for use in avariety of fields.

According to the present invention, there are provided a method ofmanufacturing a semiconductor device and a substrate processingapparatus, which are designed to modify a conventional film so as toimprove the quality of the film for achieving a desired performancelevel of a semiconductor device.

SUPPLEMENTARY NOTE

The present invention also includes the following embodiments.

(Supplementary Note 1)

According to an embodiment of the present invention, there is provided amethod of manufacturing a semiconductor device, the method including:

forming a first layer including a first element on a substrate bysupplying a gas containing the first element to an inside of a processvessel in which the substrate is accommodated under a condition where achemical vapor deposition (CVD) reaction is caused;

forming a second layer including the first element and a second elementby supplying a gas containing the second element to the inside of theprocess vessel to modify the first layer; and

forming a thin film including the first and second elements and having apredetermined thickness by setting the forming of the first layer andthe forming of the second layer to one cycle and repeating the cycle atleast once,

wherein pressure of the inside of the process vessel, or pressure of theinside of the process vessel and a time of supplying the gas in oneprocess of the forming of the first layer and the forming of the secondlayer are controlled to be higher or longer than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the one process when the thin filmhaving a stoichiometric composition is formed, or

pressure of the inside of the process vessel, or pressure of the insideof the process vessel and a time of supplying the gas in the otherprocess of the forming of the first layer and the forming of the secondlayer are controlled to be lower or shorter than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the other process when the thin filmhaving the stoichiometric composition is formed,

so as to form the thin film having a composition that one of the firstand second elements of the thin film is excessive as compared with theother in terms of the stoichiometric composition.

(Supplementary Note 2)

According to another embodiment of the present invention, there isprovided a method of manufacturing a semiconductor device, the methodincluding:

forming a first layer including a first element on a substrate bysupplying a gas containing the first element to an inside of a processvessel in which the substrate is accommodated under a condition where aCVD reaction is caused;

forming a second layer including the first element and a second elementby supplying a gas containing the second element to the inside of theprocess vessel, wherein the second layer is formed by forming a layerincluding the second element on the first layer, or the second layer isformed by modifying the first layer;

forming a third layer including the first element, the second element,and a third element by supplying a gas containing the third element tothe inside of the process vessel to modify the second layer; and forminga thin film including the first to third elements and having apredetermined thickness by setting the forming of the first layer, theforming of the second layer, and the forming of the third layer to onecycle and repeating the cycle at least once,

wherein pressure of the inside of the process vessel, or pressure of theinside of the process vessel and a time of supplying the gas in oneprocess of the forming of the first layer, the forming of the secondlayer, and the forming of the third layer are controlled to be higher orlonger than pressure of the inside of the process vessel, or pressure ofthe inside of the process vessel and a time of supplying the gas in theone process when the thin film having a stoichiometric composition isformed, or

pressure of the inside of the process vessel, or pressure of the insideof the process vessel and a time of supplying the gas in the otherprocess of the forming of the first layer, the forming of the secondlayer, and the forming of the third layer are controlled to be lower orshorter than pressure of the inside of the process vessel, or pressureof the inside of the process vessel and a time of supplying the gas inthe other process when the thin film having the stoichiometriccomposition is formed,

so as to form the thin film having a composition that one of the firstto third elements of the thin film is excessive as compared with theothers in terms of the stoichiometric composition.

(Supplementary Note 3)

According to another embodiment of the present invention, there isprovided a method of manufacturing a semiconductor device, the methodincluding:

forming a first layer including a first element on a substrate bysupplying a gas containing the first element to an inside of a processvessel in which the substrate is accommodated under a condition where aCVD reaction is caused;

forming a second layer including the first element and a second elementby supplying a gas containing the second element to the inside of theprocess vessel, wherein the second layer is formed by forming a layerincluding the second element on the first layer, or the second layer isformed by modifying the first layer,

forming a third layer including the first element, the second element,and a third element by supplying a gas containing the third element tothe inside of the process vessel, wherein the third layer is formed byforming a layer including the third element on the second layer, or thethird layer is formed by modifying the second layer;

forming a fourth layer including the first to third elements and afourth element by supplying a gas containing the fourth element to theinside of the process vessel to modify the third layer; and

forming a thin film including the first to fourth elements and having apredetermined thickness by setting the forming of the first layer, theforming of the second layer, the forming of the third layer, and theforming of the fourth layer to one cycle and repeating the cycle atleast once,

wherein pressure of the inside of the process vessel, or pressure of theinside of the process vessel and a time of supplying the gas in oneprocess of the forming of the first layer, the forming of the secondlayer, the forming of the third layer, and the forming of the fourthlayer are controlled to be higher or longer than pressure of the insideof the process vessel, or pressure of the inside of the process vesselor a time of supplying the gas in the one process when the thin filmhaving a stoichiometric composition is formed, or

pressure of the inside of the process vessel, or pressure of the insideof the process vessel and a time of supplying the gas in the otherprocess of the forming of the first layer, the forming of the secondlayer, the forming of the third layer, and the forming of the fourthlayer are controlled to be lower or shorter than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the other process when the filmhaving the stoichiometric composition is formed,

so as to form the thin film having a composition that one of the firstto fourth elements of the thin film is excessive as compared with theothers in terms of the stoichiometric composition.

(Supplementary Note 4)

According to another embodiment of the present invention, there isprovided a substrate processing apparatus including:

a process vessel configured to accommodate a substrate;

a first element-containing gas supply system configured to supply a gascontaining a first element to an inside of the process vessel;

a second element-containing gas supply system configured to supply a gascontaining a second element to the inside of the process vessel;

a pressure regulating unit configured to control pressure of the insideof the process vessel; and

a controller,

wherein the controller is configured to control the pressure regulatingunit, the first element-containing gas supply system, and the secondelement-containing gas supply system so as to:

form a first layer including the first element on the substrate bysupplying the gas containing the first element to the inside of theprocess vessel in which the substrate is accommodated under a conditionwhere a CVD reaction is caused;

form a second layer including the first element and the second elementby supplying the gas containing the second element to the inside of theprocess vessel to modify the first layer; and

form a thin film including the first and second elements and having apredetermined thickness by setting the forming of the first layer andthe forming of the second layer to one cycle and repeating the cycle atleast once,

wherein pressure of the inside of the process vessel, or pressure of theinside of the process vessel and a time of supplying the gas in oneprocess of the forming of the first layer and the forming of the secondlayer are controlled to be higher or longer than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the one process when the thin filmhaving a stoichiometric composition is formed, or

pressure of the inside of the process vessel, or pressure of the insideof the process vessel and a time of supplying the gas in the otherprocess of the forming of the first layer and the forming of the secondlayer are controlled to be lower or shorter than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the other process when the thin filmhaving the stoichiometric composition is formed,

so as to form the thin film having a composition that one of the firstand second elements of the thin film is excessive as compared with theother in terms of the stoichiometric composition.

(Supplementary Note 5)

According to another embodiment of the present invention, there isprovided a substrate processing apparatus including:

a process vessel configured to accommodate a substrate;

a first element-containing gas supply system configured to supply a gascontaining a first element to an inside of the process vessel;

a second element-containing gas supply system configured to supply a gascontaining a second element to the inside of the process vessel;

a third element-containing gas supply system configured to supply a gascontaining a third element to the inside of the process vessel;

a pressure regulating unit configured to control pressure of the insideof the process vessel; and

a controller,

wherein the controller is configured to control the pressure regulatingunit, the first element-containing gas supply system, the secondelement-containing gas supply system, and the third element-containinggas supply system so as to:

form a first layer including the first element on the substrate bysupplying the gas containing the first element to the inside of theprocess vessel in which the substrate is accommodated under a conditionwhere CVD reaction is caused;

form a second layer including the first and second elements by supplyingthe gas containing the second element to the inside of the processvessel, wherein the second layer is formed by forming a layer includingthe second element on the first layer, or the second layer is formed bymodifying the first layer;

form a third layer including the first element, the second element, andthe third element by supplying the gas containing the third element tothe inside of the process vessel to modify the second layer; and

form a thin film including the first to third elements and having apredetermined thickness by setting the forming of the first layer, theforming of the second layer, and the forming of the third layer to onecycle and repeating the cycle at least once,

wherein pressure of the inside of the process vessel, or pressure of theinside of the process vessel and a time of supplying the gas in oneprocess of the forming of the first layer, the forming of the secondlayer, and the forming of the third layer are controlled to be higher orlonger than pressure of the inside of the process vessel, or pressure ofthe inside of the process vessel and a time of supplying the gas in theone process when the thin film having a stoichiometric composition isformed, or

pressure of the inside of the process vessel, or pressure of the insideof the process vessel and a time of supplying the gas in the otherprocess of the forming of the first layer, the forming of the secondlayer, and the forming of the third layer are controlled to be lower orshorter than pressure of the inside of the process vessel, or pressureof the inside of the process vessel and a time of supplying the gas inthe other process when the thin film having the stoichiometriccomposition is formed,

so as to form the thin film having a composition that one of the firstto third elements of the thin film is excessive as compared with theothers in terms of the stoichiometric composition.

(Supplementary Note 6)

According to another embodiment of the present invention, there isprovided a substrate processing apparatus including:

a process vessel configured to accommodate a substrate;

a first element-containing gas supply system configured to supply a gascontaining a first element to an inside of the process vessel;

a second element-containing gas supply system configured to supply a gascontaining a second element to the inside of the process vessel;

a third element-containing gas supply system configured to supply a gascontaining a third element to the inside of the process vessel;

a fourth element-containing gas supply system configured to supply a gascontaining a fourth element to the inside of the process vessel;

a pressure regulating unit configured to control pressure of the insideof the process vessel; and

a controller,

wherein the controller is configured to control the pressure regulatingunit, the first element-containing gas supply system, the secondelement-containing gas supply system, the third element-containing gassupply system, and the fourth element-containing gas supply system so asto:

form a first layer including the first element on the substrate bysupplying the gas containing the first element to the inside of theprocess vessel in which the substrate is accommodated under a conditionwhere a CVD reaction is caused;

form a second layer including the first and second elements by supplyingthe gas containing the second element to the inside of the processvessel, wherein the second layer is formed by forming a layer includingthe second element on the first layer, or the second layer is formed bymodifying the first layer;

form a third layer including the first to third elements by supplyingthe gas containing the third element to the inside of the processvessel, wherein the third layer is formed by forming a layer includingthe third element on the second layer, or the third layer is formed bymodifying the second layer;

form a fourth layer including the first to fourth elements by supplyingthe gas containing the fourth element to the inside of the processvessel to modify the third layer; and

form a thin film including the first to fourth elements and having apredetermined thickness by setting the forming of the first layer, theforming of the second layer, the forming of the third layer, and theforming of the fourth layer to one cycle and repeating the cycle atleast once,

wherein pressure of the inside of the process vessel, or pressure of theinside of the process vessel and a time of supplying the gas in oneprocess of the forming of the first layer, the forming of the secondlayer, the forming of the third layer, and the forming of the fourthlayer are controlled to be higher or longer than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the one process when the thin filmhaving a stoichiometric composition is formed, or

pressure of the inside of the process vessel, or pressure of the insideof the process vessel and a time of supplying the gas in the otherprocess of the forming of the first layer, the forming of the secondlayer, the forming of the third layer, and the forming of the fourthlayer are controlled to be lower or shorter than pressure of the insideof the process vessel, or pressure of the inside of the process vesseland a time of supplying the gas in the other process when the thin filmhaving the stoichiometric composition is formed,

so as to form the thin film having a composition that one of the firstto fourth elements of the thin film is excessive as compared with theothers in terms of the stoichiometric composition.

What is claimed is:
 1. A method of manufacturing a semiconductor device,the method comprising forming a thin film having a predeterminedthickness and a predetermined composition on a substrate, the thin filmcomprising a first element and a second element different from the firstelement, by repeating a cycle a plurality of times, the cyclecomprising: (a) forming a first layer comprising the first element andhaving a thickness of several atomic layers or less than one atomiclayer on the substrate by supplying a gas containing the first elementinto a process vessel accommodating the substrate; and (b) forming asecond layer comprising the first element and the second element bysupplying a gas containing the second element into the process vessel tomodify the first layer without saturating a modifying reaction of thefirst layer by the gas containing the second element.
 2. The method ofclaim 1, wherein each of the steps (a) through (b) is carried out undera non-plasma, heated and decompressed atmosphere.
 3. The method of claim1, wherein only a surface layer of the first layer having the thicknessof several atomic layers is modified in the step (b).
 4. The method ofclaim 1, wherein only a part of a surface layer of the first layerhaving the thickness of several atomic layers is modified in the step(b).
 5. The method of claim 1, wherein only a part of the first layerhaving the thickness of less than one atomic layer is modified in thestep (b).
 6. A method of manufacturing a semiconductor device, themethod comprising forming a thin film having a predetermined thicknessand a predetermined composition on a substrate, the thin film comprisinga first element, a second element different from the first element and athird element different from the first element and the second element,by repeating a cycle a plurality of times, the cycle comprising: (a)forming a first layer comprising the first element and having athickness of several atomic layers or less than one atomic layer on thesubstrate by supplying a gas containing the first element into a processvessel accommodating the substrate; (b) forming a second layercomprising the first element and the second element by supplying a gascontaining the second element into the process vessel to form adiscontinuous layer comprising the second element on the first layer orto modify the first layer without saturating a modifying reaction of thefirst layer by the gas containing the second element; and (c) forming athird layer comprising the first element, the second element, and thethird element by supplying a gas containing the third element into theprocess vessel to modify the second layer without saturating a modifyingreaction of the second layer by the gas containing the third element. 7.The method of claim 6, wherein each of the steps (a) through (c) iscarried out under a non-plasma, heated and decompressed atmosphere. 8.The method of claim 6, wherein only a surface layer of the second layeris modified in the step (c).
 9. The method of claim 6, wherein only apart of a surface layer of the second layer is modified in the step (c).10. A method of manufacturing a semiconductor device, the methodcomprising forming a thin film having a predetermined thickness and apredetermined composition on a substrate, the thin film comprising afirst element, a second element different from the first element, athird element different from the second element and a fourth elementdifferent from the first element, the second element and the thirdelement, by repeating a cycle a plurality of times, the cyclecomprising: (a) forming a first layer comprising the first element andhaving a thickness of several atomic layers or less than one atomiclayer on the substrate by supplying a gas containing the first elementinto a process vessel accommodating the substrate; (b) forming a secondlayer comprising the first element and the second element by supplying agas containing the second element into the process vessel to form adiscontinuous layer comprising the second element on the first layer orto modify the first layer without saturating a modifying reaction of thefirst layer by the gas containing the second element; (c) forming athird layer comprising the first element, the second element and thethird element by supplying a gas containing the third element into theprocess vessel to form a discontinuous layer comprising the thirdelement on the second layer or to modify the second layer withoutsaturating a modifying reaction of the second layer by the gascontaining the third element; and (d) forming a fourth layer comprisingthe first, the second element, the third element and the fourth elementby supplying a gas containing the fourth element into the process vesselto modify the third layer without saturating a modifying reaction of thethird layer by the gas containing the fourth element.
 11. The method ofclaim 10, wherein each of the steps (a) through (d) is carried out undera non-plasma, heated and decompressed atmosphere.
 12. The method ofclaim 10, wherein only a surface layer of the third layer is modified inthe step (d).
 13. The method of claim 10, wherein only a part of asurface layer of the third layer is modified in the step (d).
 14. Amethod of processing a substrate, the method comprising forming a thinfilm having a predetermined thickness and a predetermined composition onthe substrate, the thin film comprising a first element and a secondelement different from the first element, by repeating a cycle aplurality of times, the cycle comprising: (a) forming a first layercomprising the first element and having a thickness of several atomiclayers or less than one atomic layer on the substrate by supplying a gascontaining the first element into a process vessel accommodating thesubstrate; and (b) forming a second layer comprising the first elementand the second element by supplying a gas containing the second elementinto the process vessel to modify the first layer without saturating amodifying reaction of the first layer by the gas containing the secondelement.
 15. A method of processing a substrate, the method comprisingforming a thin film having a predetermined thickness and a predeterminedcomposition on the substrate, the thin film comprising a first element,a second element different from the first element and a third elementdifferent from the first element and the second element, by repeating acycle a plurality of times, the cycle comprising: (a) forming a firstlayer comprising the first element and having a thickness of severalatomic layers or less than one atomic layer on the substrate bysupplying a gas containing the first element into a process vesselaccommodating the substrate; (b) forming a second layer comprising thefirst element and the second element by supplying a gas containing thesecond element into the process vessel to form a discontinuous layercomprising the second element on the first layer or to modify the firstlayer without saturating a modifying reaction of the first layer by thegas containing the second element; and (c) forming a third layercomprising the first element, the second element and the third elementby supplying a gas containing the third element into the process vesselto modify the second layer without saturating a modifying reaction ofthe second layer by the gas containing the third element.
 16. A methodof processing a substrate, the method comprising forming a thin filmhaving a predetermined thickness and a predetermined composition on thesubstrate, the thin film comprising a first element, a second elementdifferent from the first element, a third element different from thesecond element and a fourth element different from the first element,the second element and the third element, by repeating a cycle aplurality of times, the cycle comprising: (a) forming a first layercomprising the first element and having a thickness of several atomiclayers or less than one atomic layer on the substrate by supplying a gascontaining the first element into a process vessel accommodating thesubstrate; (b) forming a second layer comprising the first element andthe second element by supplying a gas containing the second element intothe process vessel to form a discontinuous layer comprising the secondelement on the first layer or to modify the first layer withoutsaturating a modifying reaction of the first layer by the gas containingthe second element; (c) forming a third layer comprising the firstelement, the second element and the third element by supplying a gascontaining the third element into the process vessel to form adiscontinuous layer comprising the third element on the second layer orto modify the second layer without saturating a modifying reaction ofthe second layer by the gas containing the third element; and (d)forming a fourth layer comprising the first element, the second element,the third element and the fourth element by supplying a gas containingthe fourth element into the process vessel to modify the third layerwithout saturating a modifying reaction of the third layer by the gascontaining the fourth element.